It will be the GOP to change/morph/die out. The Dem's are well on the way to becoming a socialist immigrant/minority party with nothing in sight to check that.
Possibly, but I'm not sure the Dems are as healthy and unified as you portray them. The way I see things, there are deep divisions within them. I count no less than four different ideological factions on the left. Sometimes they overlap, but often they are opposed. These are broad brushes, of course, and you can probably break it down quite further.
1. You've got your basic Neoliberal, many of which are associated with Hillary, corporate corruption, elitism, and war hawking. This group seems to be falling out of favor, and many more extreme Dems consider them basically no better than (neo-con) Republicans.
2. Economic Socialists. This is your Bernie Bro, tax the rich, free college for all, universal health care crowd. Sieze the means of production! They feel deeply betrayed by group 1, who they blame for stealing the election.
3. "Progressive" Cultural Warriors. Smash the Patriarchy, down with Whitey, and Bash the Fasch. This is a vast swath of guilt-laden college educated middle class people. There's a lot of overlap between 2 and 3, but also between 1 and 3, and probably a lot of 3 that disagrees with both 1 and 2. In some ways, these were the pawns that Bernie and Hilary were fighting over. This group is also prone to purity spiraling, and eating there own.
4. "Classical Liberals". These are basically the left's version of libertarian, and the left has been hemmoraging them like crazy. Free speech is a big issue with them right now. They don't really like the Right, but as individualists, they also don't agree with the Marxist lenses of 2 or 3, and they see 1 as basically corrupt out of touch elites, so many of them ended up voting Trump for lack of anything better. They feel abandoned by the left (who calls them Nazi sympathizers), but it's likely some would return to it if there were a non-corrupt, non-marxist Dem candidate running against, say, an evangelical Republican. OTOH, a lot of these are probably among the newly "woke" ones that
@andrew alludes to, contributing to the Libertarian Party's growth.