Microsoft/Nokia can continue to lead in optics if it continues to prioritize the camera and, when push comes to shove, avoid compromising on decisions involving optical tech. The hardest challenge for any camera experts at Apple will be that, when push comes to shove, Apple will choose form over function. In the same way that Jobs abhorred physical buttons, I'm pretty a Lumia-like camera "hump" would be out of the question.
That said, constraints like that can force innovation: how can we get the same camera performance without the hump? For the foreseeable future, there will be a physics element to camera tech given the lens. But it's going to become more about the camera software than the lens: at some point, the software might be smart enough to know how the picture should look regardless of any technical "user-related" errors in how the picture was taken. HDR is a step in this direction.