I think your scenario is very likely to play out, but in my mind the GOP won’t die, they will simply merge the neocons and neolibs into a formal pro-corporate party. Once the people have an actual left-of-center party to vote for that champions workers rights and other populist policies unencumbered, the political dynamics will shift very rapidly. This is why it has taken so long to occur - the dog and pony show of fake opposition prevents us from having that choice entirely.