Re: We don't *know*, but we are pretty sure it does
A major re-think like that might explain a lot, but since we have no data that would shape what that rethink should be, we cannot start it now
Sightly too strong. If a theory of everything exists that supercedes both quantum mechanics and gravitation, it might be concieved of tomorrow by a mathematician of genius. If it were simpler than the existing two irreconcilables, I'd wager Occam's razor that it was right. And it would probably make predictions which were at odds with one or other of the existing theories, which would then help the experimentalists know what to look for.
It wouldn't be the first time that the theory came first and observations that confirm the theory later.
Some might say that the theory *has* to come first, otherwise the universe wouldn't know what to do. And a few would say that it didn't, until something somewhere started thinking. Philosophy, again.