As for me, I believe hope springs eternal. People change. Times change. When the Federalists collapsed, the Whigs rose to take their place. When the Whigs lost their principles, along came the Republicans.
The GOP is the second-oldest political party in the world. The Democrats are the only one older. Perennial two-party systems that last a century and a half are the exception, not the norm.
Conservatism faces a challenge, to be sure, and you may be right—the Republican Party faces a dire future. But as I said, we are all rational human beings. Another poster once noted: lily-white midwestern states like Minnesota and Wisconsin vote Democrat in federal elections consistently, while majority-minority Texas is still solidly conservative. Demography is NOT destiny.