Now they'll all move to the Democratic Party!
Depolarization would definitely keep both parties alive. It could be the start of a detente but no one would be happy. There is a reason so few loyal yellow dogs and gypsy moths remain.
I don't think the socons are going anywhere. They will simply change their orientation and who they ally themselves with. In the Bush years, it was an Evangelical movement that allied itself with the neoconservative movement to build a globalistic "compassionate conservative" coalition that made immigrant groups competitive. Now, they see that they are losing their kids for not much ground in battle (the military seems to be their version of college for those that can get into it but not the best private schools). So now they are looking for a more organic alliance with the alt-Right to protect their interests without the need for more traditional benefits that they oppose. "Replace the social safety net and labor regulations with tariffs and infrastructure spending".