It's all or nothing in this particular case. And the states have a very powerful argument that the current law is unconstitutional. I suspect that in June of next year, if not sooner, the whole of Obamacare will be struck down with all the fallout that entails.
As for a plan. I sure would hope Trump and GOP allies have thought this through and have one in place.
One of my coworkers has a favorite expression - Hope is not a strategy. Right now the GOP has nothing, and little evidence that one is being worked on.
I suspect sometimes that nothing is what the GOP does best.