100% vegan? Very unlikely. 95% vegan in the developed world? Possibly.
Here is the deal. First, it's at least 50/50 that all of human civilization will be destroyed by nuclear war in the next century. It's a miracle that nukes haven't been used since WWII, but it's only a matter of time, and with Trump saber-rattling about the nuclear stockpile, it could be sooner than anyone imagines. If it happens and it gets out of control, all of civilization will be destroyed, with only pockets of humans left near the equator, where the nuclear winter will have least effect, foraging for whatever food they can find.
But say we're lucky and that doesn't happen. Then we're still looking at major disruption from climate change. The effects will be terrible, but human civilization will almost certainly survive, though with large loss of life and by necessity on higher ground. Still, developed nations will probably be able to survive in something like their current form.
If that is the case, I would expect to see a slow transition away from animal agriculture. For one thing, there will be less land after the seas rise, so setting aside huge tracts to graze cattle will be less feasible. For another thing, synthetic alternatives, including lab-grown, will become available and be much better than the current faux meats and cheeses. Cost will probably be the driving force, more than ethics and animal rights, though ethics and the animal rights movement will play at least some part in putting political pressure on the animal agriculture industry.
I'd expect to see much of the meat and dairy production shift to synthetic alternatives over the next 25-100 years. I seriously doubt, though, that it will ever be 100%. It's like horses. 100 years ago, they were the primary mode of transportation. However, cheaper and more efficient non-animal-based transportation became available, and horses have been largely displaced. Still, there are some horses used for transportation, even in the developed world. I'd expect to see a similar situation with the food industry over the next 100 years or so.
Finally, in contrast to the developed world, in the developing world, I doubt there will be much change, especially among hunter-gatherer communities and subsistence farmers. I doubt those communities will do much to restrict their use of dietary animal products.
Last edited by Dilettante; 12-24-2016 at 10:36 AM.