It's difficult to predict where the GOP will go, but I think the Democratic party will continue it's current trajectory of neoliberal economic policies favored by their new base of UMC degree holders and social liberalism favored by their old base of younger and diverse working classes and students.
The likeliest path for the GOP is to get lost in the wilderness after losing 2020 and 2024, which I'd obviously like to avoid. It needs to simultaneously become more pro-worker/skeptical of corporate powers, address student debt, climate change and cost of living in urban/suburban areas, while remaining hawkish on immigration and geopolitics (China) if it wants to remain relevant. Considering Ronna McDaniel is retaining the GOP's 2016 platform for 2020, I don't have much faith in the party leadership to read tea leaves and adopt to a changing world.
I agree with pretty much everything you said. In addition to that, GOP might need to slightly moderate on immigration (pro-DACA, and if the border gets secured at some point then pro-pathway AFTER the border is strongly secured. Some exit polling bears that out) and racial issues. They should definitely not take the 1619 Project/the BLM organization route but acknowledging that racism is still a current problem, more criminal justice reform for nonviolent offenses, stopping the Confederate flag stuff, and stating that Black Lives Matter (while not endorsing the organization's platform) may help. GOP should remain the more vocally patriotic party though. Going libertarian (but not progressive) on most non-abortion social issues would probably do the best job of appealing to new voters while not losing their current socially conservative base. Economically, be anti-socialism/Medicare for All/Green New Deal/massive tax increases but doctrinaire fiscal conservatism is politically and practically infeasible. Be more open to infrastructure spending and maybe a basic public option for those who absolutely need it. Party's base would probably be working-to-middle class and somewhat more diverse than it is now.
Democrats will become the party of the upper middle class (outside of some ruby red GOP Southern and Midwestern suburbs) and poor, uniformly socially progressive (some more socially moderate and not as "woke" Black and Hispanic voters would go to the GOP in this scenario). Will maintain huge margins among Millennials and college educated white women. Candidates with Pete Buttigieg-esque politics (but with more non-white appeal) will be the norm. There will be a growing DSA-eque wing though, especially in very blue cities and college towns.
