I totally agree that Skecth is not a silver bullet. UX is a far more complex subject than only static resources. The tools of the future should empower designers to reproduce their whole vision of the product, such as micro-interactions, animations and so on. Obviously, there’s a lot of tools that allows such things but it doesn’t generate real code that could, at least, allow developers to use the designer’s process as a starting point for their work. This means that, most of the time, the designer’s work is a waste of time in a collaborative environment.
IMHO, the right way to build UI (a huge part of the UX chain) is with declarative code. On the web we have HTML and CSS. But in the mobile world there’s nothing like that. I think that tools like Fuse (fusetools.com) are shaping the future in the right direction.
This endless discussion about “designers that knows how to code” and “developers that are also designers” makes no sense and doesn’t solve the real problem. People are worried about their role in the process when they should be worried about the process itself.