Florida is likely a lost cause (between conservative minorities and the elderly), but you don’t need Florida to win national elections (clearly). If the electoral college is done away with, it’s also moot, as there is enough popular vote margin at the national level to always go blue.
And with Trump showing that it's possible to increase the Republican vote share among minorities... I'd expect political strategists to focus more effort there in the future. A self-fulfilling prophecy, in a way.
Sorry my thesis wasn't clear, although I appreciate the opportunity to refine the message. Better to get the kinks out here before speaking to an audience IRL.
Losing a solid voter base might mean that the Republicans need to change their platform to appeal to more voters, but it doesn't mean that they're forever doomed and will never win another election. Maybe that means compromising on abortion. Maybe it means immigration reform - but from the Republican perspective, and not giving amnesty to illegal immigrants. (And funnily enough, IIRC amnesty isn't particularly popular among LEGAL immigrants) Maybe it means pulling their heads out of their asses re: climate change, and running on a revenue-neutral carbon tax.
All of this means changes, but not an end to the party.
As you said, neither party is going away, but they will both have to change to accommodate an evolving electorate. As someone said upthread, both parties need to stop taking their voters for granted and go out and listen to them.
[1] https://www.pewresearch.org/politics/2018/06/28/shifting-pub...
[2] https://www.pewresearch.org/politics/2019/08/29/u-s-public-c...
[3] https://www.pewsocialtrends.org/2019/03/21/retirement-social...
[4] https://www.pewresearch.org/fact-tank/2020/09/29/increasing-...
[5] https://www.pewresearch.org/fact-tank/2018/10/03/most-contin...