As a Gen-X former generally Republican voter (I always crossed the aisle for particular candidates -- hell, the first campaign I worked for was Mark White's v. Bill Clements), I'll never go back to the GOP. Ever. I honestly can't conceive of a world where I'd even cross the aisle to vote for a particularly "meritorious" GOP candidate in a downballot race. Because what the GOP has done, and chosen to be, is unforgivable to me. Saying someone is a good GOP politician is, to me, like saying that "I know he's a member of a racist death cult, but he has some good ideas about transportation." It's a non-starter. Being a member of the GOP is evidence of a completely disqualifying character flaw.
My kids will never vote GOP. Even my son, who is reasonably conservative (relative to the rest of the family) is left-of-center. And he's politically-minded (as a vocation). He may be the future of the "moderate" wing of the Democratic party, and I can tell you that he accepts a lot of things we old farts might call "progressive" as being rather mainstream.
Future democrats are going to be much more "progressive" than current ones. That's being baked in by the political climate of the past 10+ years and the current situation. Contrast the core message of Obama's speech last night -- we have to look out for each other, and serving the common good has to be part of our calculus -- versus the shouted refrain from the right of "ME, ME, MINE!", and the contrast couldn't be more stark. A shitload of younger voters are more community and society-minded. They hold the radical idea that maybe we should give a shit about our fellow man, not just ourselves. And that foundational belief is very compatible with progressive ideas. We've gone all-in on the church of the individual, and we are reaping the whirlwind of that right now. They aren't going to forget. Ever.