It's too early to say honestly, as I can see both party coalitions going a variety of way depending on how the next two to three elections go. I can see a few scenarios:
1. Politics continue to be dominated by cultural/social issues, but the GOP gets it sh**t together when it comes to minority outreach due demographics. In this case, poorer, socially conservative Black and Latino voters (particularly black and latino men) start trending heavily Republican if the the GOP returns to a Bush era immigration stance (or as close to it as possible) while continuing down a populist path Post Trump. Asian voters however continue to trend heavily Democratic, while the White vote is split by gender, with white women going overwhelmingly Democratic, while white men (minus post grads and odd balls like me) becoming even more Republican. Both parties are economically populist in one form or another.
2. The GOP gets beat the out at the Presidential level through the 2020s and you see a party system that somewhat resembles the 5th party system. The Democrats become a socially liberal version of the New Deal era Democratic party, while the Republicans, after a string of defeats for the Presidency and, more often than not, the House, emerge as a center right check and balance on a dominant Democratic party. This assumes though that a 6-3 Conservative Supreme Court doesn't completely rig the deck in the favor of the Republicans against the will of the people.
3. Both parties continue to go into the fringes, racial tensions continue to increase, and the country becomes even more tribal and polarized. Both parties change the rules and laws each time they have the Presidency and Congress (court packing, legislative process/rules, etc..) for the sake of political gain and trying to secure power for themselves, officially and permanently destroying our democracy and institutions in the process. Basically late 6th party system (2010-Present) on steroids. This definitely happens if Trump gets a second term, but there's a decent chance this happens after a Biden win to.
I concur with much of this though I don't actually think a pro-immigration stance would help the GOP that much if at all, though a softening of rhetoric would probably be beneficial. Immigrant communities especially those who have been established for at least a few generations actually tend to be fairly sceptical about new immigration, look at how well Trump did with established Hispanic communities in Southern Colorado for example. I also seriously doubt the kind of African-American voter that the GOP should be trying to win over has immigration particularly high up their priority list either.
Doing better with minority voters is much more about shedding their 'white grievance' reputation, dropping dog-whistle racism and making a concerted effort to make minority voters feel included in their 'America-first' vision of the country. The 'Ford-nation' blueprint is an example of how they could go about doing this.
I think that there is a fair chance that the USA is entering a period of Democratic dominance where the GOP really struggles to make headway (paralleling the Republican ascendancy in the Reagan years). Though all things come to an end and the Democrats will eventually alienate one or more of their core voting groups whilst the GOP will have adjusted their platform enough to appeal to these people. Given the composition of the Republican base and their utter hatred of the 'liberal elite', I find it very difficult to see them going back to Rockerfeller Republicanism to appeal to well of suburban moderates. More likely, they just completely drop the race stuff and the GOP in 25 years time looks to be a refined version of Trumpism with a much, much less white (or orange) face. The Kim Klaciks of this world are the party's future IMO, with as others said, education level being a better predictor of political leanings than race.
Whilst I do agree there will be at least a moderate sized gender gap in voting, I think it's quite unlikely that it will be anywhere near as big as many of the above contributors are predicting. This is because peoples' political opinions are strongly influenced by those around them. Seen as men and women mingle/socialise far more with each other than minority groups with extreme voting patterns tend to do with people outside of their group, (usually a factor of living/growing up in an area primarily populated by people of your own background, societal prejudice or shared religious values e.g. evangelicals) it is very unlikely that the conditions for an extreme gender based voting patterns could ever be met.
