I can't see "let's ignore ethnics and let's get >70% of the white vote" working effectively.
Me ether,
I also see Rockefeller's prediction as unlikely due to the fact that there in fact is a generational change about to happen within the GOP.
Let me explain,
Most of these hard-right SoCo flavored Republicans and Tea Party members who hate "Obama, Big government, Sharia Law, Abortion, GAys, and the Messicans" are typically above the age of 55 or at least above 48. So unlike what happened with the Democrats hard turn to the left in the 1970's driven by youth involvement in the Civil Rights and Anti-War movements. These peoples political staying power's rather limited and is waning in the long run.
The much younger generation of conservatives replacing them I.e. those in their 20's to 40's are for the most part in my experience classic moderate Republicans or hard-libertarians. As they could care less about the cultural wars and many of them openly support gay rights and legalizing pot and don't come across as anti-immigrant. What SoCos there are amongst the new generation try to sway away from the old culture war issues. So the hard right is clearly in the minority Imo in the future GOP.