I would really hope for "only web browsers left". But then they wouldn't be web browsers, instead they would be the operating systems standards, like POSIX. I hate the scenarios that goes like this - "Hey I have an idea for a software, ok cool lets build it, but wait, what platform should we target?". A software is just a bunch of computations that interact with IO devices. why can't we have a standard way to do that?

I hope so too. Yes there wouldn't be web browsers in the sense that you are writing. I like how a 'browseros' could basically treat software itself as a plug-in where it relegates itself to being an IO device for software. Seems very simple and modular.

False dichotomy? Is there a reason that you believe only these two outcomes are possible?

Definitely it is, but what outcome would you prefer and why?