First of all, there are two different theories of relativity. The simpler one is Special Relativity (SR), which combines space and time into a single entity, and is mostly used to describe what happens when things move very fast. All of modern physics is consistent with SR. On the other hand, you also have General Relativity (GR), which contains all of SR, and also describes how mass interacts with spacetime, thus producing gravity. The current theory of GR is *not* consistent with the current theory of quantum mechanics, so in order to unify them, one or both will need to be changed somehow. And there must be some sort of unification: When, for instance, a black hole evaporates down to a sufficiently small mass (just how small is “sufficiently” is not known, but a good guess is around the Planck mass), *something* has to happen, but we don’t know yet just what that something would be.

I’m not sure that the concept of duality is a useful one here: When you’re working with quantum mechanics, you don’t care whether you’re describing waves or particles. You do all the math the same way, and then, at the end, you decide whether waves or particles will be more convenient for expressing your answer. With GR and QM, though, it’s not just a matter of description: The intervening math is completely different.