I think it'll be hard to ever move away from flat design, because everyone else does it, and it's associated with modernity, while skeuomorphism is associated with old software.

I don't have hard numbers, but I think flat design really became a lot more popular after Windows 8 was released. For a while, Windows 8 was heavily criticized for its UI design (and not just because it was flat), but they stuck with flat design the entire time, and I believe they had a great role in popularizing it.

I guess we'll just need someone else to make their UIs more realistic and 3D, like the old ones used to be, and stick with it no matter what others say, and the style may become popular again if their UI is in wide use.