They either turn out their base, or they turn off their base. All the folderol about "Congressional hypocrites" and "electing Democrats" aside, if the GOP hierarchy keeps thinking and acting like it's the base's fault instead of their fault (and the fault of their idiotic anti-conservative policies and proposals) that the GOP loses elections, they'll turn off their base for good, and all this discussion about whether the base turns out for the Republican ticket will be a fond dream.
I don't see the Republican Party faring too well in your scenario. If shunning conservatives is what today's GOP is all about then they will lose more than just the conservative vote over time. There are millions of moderates in the party that indirectly benefit from the conservative influence in the party. Without that influence the GOP will move so far left it will alienate even the so-called moderates. At that point there will be virtually no difference between the parties.