[dripton]

Maybe.

cpyext is a hack to let PyPy run Python/C API modules. It works for some, but not all, and it's slow. I'm sure it'll keep getting better, but not sure if it'll ever be good enough to run PyGTK or PyQt.

PyPy has good support for ctypes, so ctypes bindings are a good option. There are projects out there like pygir-ctypes and ctypes-gtk. One of them just needs to become complete enough to be a good choice for GTK programming. Compatibility with new PyGObject is more likely than compatibility with legacy PyGTK, though.

PyQt is harder because it's C++.