If by plausible, you mean that can (and will) happen, here are my super optimistic predictions.
Europe will dissolve, and turn into a series of even more xenophobic states than they are now, which includes the UK as well.
USA will balkanize, so will Brazil. Basically, massive ethnic/racial, political, and socio-economic divides that will worsen over time.
Africa will descend into anarchy, and not the good kind; and will become uninhabitable.
South East Asia has dozens of ethnicities, several religions, and poor economic conditions that will also cause this part of the world to fall into chaos. Also will become uninhabitable.
Australia will keep being the xenophobic puppet of the USA.
New Zealand will keep being Australia's puppet.
India will have a civil war. You can't have 50% of nationalists, and no pushback at all. And if it somehow avoids that, a war will errupt between them and Pakistan over some petty shit. Also will be hit with massive refugee -waves because Bangladesh will simply cease to exist if water levels rise a few meters higher. And will become uninhabitable.
China might survive despite all the shit going on, Russia might go deeper into failed state territory; or elect a communist government.
The Levant will keep being plunged into civil wars. Iran might survive.
The arabic peninsula will become hostile to human life.
A good chunk of the Island nations will cease to exist, too bad the UK will still be around.
All the reasons are the ones we already know. Climate change creating, and worsening problems for mankind. Food and water supply, disease, mineral over-extraction, soil pollution, biodiversity death, natural catastrophes, water levels rise, end of Albedo effect, and so on. Everything I mentioned before will result in hundreds of millions dead, if not billions on the long term. There ya go champ, this doesn't get any more cursed than this.
If by plausible, you mean that can (and will) happen, here are my super optimistic predictions.
All the reasons are the ones we already know. Climate change creating, and worsening problems for mankind. Food and water supply, disease, mineral over-extraction, soil pollution, biodiversity death, natural catastrophes, water levels rise, end of Albedo effect, and so on. Everything I mentioned before will result in hundreds of millions dead, if not billions on the long term. There ya go champ, this doesn't get any more cursed than this.