On land probably we will not succeed. It gets a bit crowded with 10 billion, the available land per capita is decreasing, we resist giving up some of our wealth , our thirst for materials and technology. The battle of resources has started. Even the UN admits this implicitly, as Alice Friedmann concludes on the basis of the recent UN report on global resources:
“ The UN doesn’t flat out state there are limits to growth, though they come close when they point out there’s not enough stuff in the world to raise the standard of living for everyone and we appear to be on an unsustainable trajectory.  The actual paragraph that she hints to is: : It indicates that the level of development and well-being in wealthy industrial countries has been achieved largely through highly resource-intensive patterns of consumption and production, which are not sustainable, even less replicable to other parts of the world”  And I can only agree with her conclusion.
However, its not only land of course, that we can consider: So, then Oceans? Back to the water, we long ago escaped from? In fact not surprising that we will move in the directions of oceans: The ocean is more or less the similar to land: man can only survive on the surface, and what is air above land is water under he oceans surface. Where birds fly over land, fish swim underneath the ocean surface ( and far out in the ocean there are no birds) . Where trees climb up in the air, weeds grow downwards.
Cultivating food near the oceans surface is in fact not different from growing on land: From agriculture to marine culture. Which probably will be one of the largest transitions we will experience. Artificially growing fish is a booming business, as well as growing seaweeds and algae. I don’t say thats the solution, its still an escape from organizing thing the right way on land, we dont solve our problem, still looking for new grounds to scavenge . But since land is occupied everywhere, we move to the sea. Its how things work….
But Then: better growing as just emptying the ocean, as fisherman do with a trawl net. That should stop, its overcroping that destroys more as it provides. Which was acceptable when we were few, and did not know. Just like nomads emptying trees. But its not of our time anymore, Fisherman should stop hunting and gathering as well, abandon steeling and plundering the seas. If a all we will start exploiting seas, we should do it decently, not like we did on land. Better use a way like permaculture, lest do it right from the start, and not leave it to some multinationals hunting fro financial profit.
Nevertheless, the ocean is already discovered as the next colonization area, and mining has started. Not all is new, we already for thousand of years have taken slat and gypsum, by evaporating basins along the coast . Now algae and sea weeds are added, and fish farms. Along the Norwegian coast there are many salmon farms, grow in huge cages by the millions. Its comparable to greenhouses on land, but the the 3D negative copy: hanging downwards in the water. Its not yet ideal, but at least its controlled growing, a kind of renewable practice. And nearly all sea bordered countries are getting into this business.
Concerning the algae , the news is still a bit misty. On one side, the yields should be enormous up to 20 tons of bio oil per hectare per year. Much more as for instance palm oil plantations. On the other side, it is a very energy intensive business, but figures lack or re protected, and no EROI is known ( energy return on energy investment) . We will have to wait and see.
Another source is sourced from the ocean: the water itself. Desalination plants are popping up everywhere ( again highly energy intensive) , it will nevertheless probably the savior of many cities along the coast not in the least Cape town, that will run dry in just a few months. 
On the energy front, tidal and gulf energy are still struggling ,the sea is untamable for these, but windturbines we already have banned to the ocean. Then who wants these in his backyard on land… Moreover, I expect, and hope) that this outdated 20 century model will soon be replaced by airborne wind, a kind of flying turbines, on cables hanging high in the air. A much more effective technology, 20 pct of material use by double output, more or less.  And he storage will be solved as well, while the wind id blowing more stable at high altitudes. The first projects have started, a English village has the scoop, on land, but they will probably move quickly to the sea, since NIMBY again and we want a free space area above land for our flying trips of course. 
So far, the developments can be overseen, its all plays down on the beaches and near shore. But that will change. The deep sea has been discovered, Blue Planet by the BBC provides us with beautiful pictures from the ocean, but there is more: The Japanese are working on harvesting Methane from the sea floor bed, . There is a lot of it, an enormous source of energy. Only its a great risk: Its not in a bubble you can drill, but compressed ans spread at the bottom of the sea, It stays there due to high pressure but in a critical balance. If that is disturbed, large clouds of methane could make it uncontrolled escape. Its lost, but worse, its a greenhouse gas, and more effective as CO2. Think of the Bermuda triangle: one of the explanations of the loss of many ships is that its an area with abundant methane, that might escape in large clouds from the sea floor. A ship ending up in such a surfacing cloud becomes hanging in the air…
A next step in the ocean is grazing for materials. Sand is known, and due to the dredging to comfort Singapore’s Concrete building boom, already some uninhabited island from the Indonesian archipelago are lost.  More interesting for industry are metals.  There are huge amounts of so called manganese nodules on the sea bed, at 4-6000meters deep, which are stony clumps , fist size, containing all kinds of metals. The first concessions are given out, and some countries are piloting the harvesting now. As far as we know, the process of nodule forming takes millions of years, and harvesting it not what you can call a renewable resource process.
You ask yourself: who owns the see? Nobody of course, or : we all together? There is hope, since there is a UN governed body that deals with a honest and fair use of the Sea, bit as I read its under heavy pressure from politicians to allow more concessions for a lot of things ( ) . While we have not the slightest idea of what risks are at stake there .And it wont surprise you that the USA has not endorsed this UN institute, and is just messing around on its own in the oceans. 
There are other ways, of course you can use ocean water and filter it to get directly some of the resources dissolved in the water, like many metals . More or less anything we are in need of is dissolved in the ocean. And as you should realize, everything available on mainland ends up in the ocean somehow sometime, its a piggy bank for all kinds of resources and organisms. But besides the unknown risks, the main problem is all these processes cost enormous amounts of energy to harvest. Fish farming and salt is relatively harmless, but filtering ocean water or deep sea mining, or treating algae is very energy intensive. And whee to get the energy? Even more windturbines and solar panels? Which will require more materials? And more energy to process, etc?
Well, anyway, we ourselves are preparing for the ocean, even to live on it: in many countries floating houses are developed. Which I call the Ark of Noah syndrome, boarding for the floods when therr will be nothing else as water… Lets things get right on land , to avoid becoming that self fulfilling prophecy , I would say.
 Cape Town water shortage: https://edition.cnn.com/2018/02/01/africa/cape-town-water-crisis-intl/
 Enerkite airborne wind: http://www.enerkite.de/technologie
 English village with airborne wind: : http://www.dailymail.co.uk/sciencetech/article-4544542/Kites-power-5-000-British-homes-2020.html
 Zand , Sand Wars, by Denis Delestrac : TED talk Delestrac: https://www.youtube.com/watch?v=VOXikTyZxPA
full documentary, (in German): https://www.youtube.com/watch?v=UGyjZnugAsQ
 Ocean resources : http://www.waterencyclopedia.com/Mi-Oc/Mineral-Resources-from-the-Ocean.html
 Circular Energy: the missing link, R.Rovers , M.Ritzen, J.Houben, V.Rovers, paper for Exergy, LCA&Sustainability conference, ELCAS 5 , Nisyros Greece, 9-11 July 2017. accesible via : https://www.researchgate.net/publication/318318419_Closing_Cycles_Circular_Energy_the_missing_link