They won't. We've all seen Priebus' memo about the GOP needing to ditch the bigotry and try to sell fiscal conservatism to a broader, more multicultural demographic. That was in 2012, and here we are.
The Republican Party had its chance to get its act together and chose to double down on becoming the party of evangelical white supremacists and failed. All we can do at this point is keep beating it down until a more moderate right wing party emerges to replace it.