'Skeuomorphism as a transitional design' is a rather misplaced monicker. If skeuomorphism is defined as using real-world elements in the digital space, then many aspects of it should never be done away with. It is much more than the green-felt Game Center, which as I say was in bad taste. It's literally everything from glossy/reflective buttons, to shadows under windows, even to windows overlapping each other as if on a physical desk. When you look at iOS7 (and windows 8) closely, you'll see it removed much more than the green felt: it removed the shadows behind icons on the Home screen; it removed all glossy images and reflections. Whereas the old Camera icon had a gorgeous glossy lens, that's been stripped away now and the new Camera icon has an image that can mean almost anything.
So no, foundational aspects of skeuomorphism cannot be considered transitional. Elements have to be distinguished from each other, and given a hierarchy, on a screen. Either you give the active element a shadow, to indicate focus, or you give it a thick crayon-colored border as Windows 8 has done. Which imho is much worse than a green felt.
XenForo seems to have been influenced by the OSX in many ways (e.g. Spotlight Search), and this includes taking many of Apple's skeuomorphic elements.
I'm looking at the shadowed buttons, which tells me they rise 'above' the plane and can be clicked on. I'm looking at the shaded 'new post' indicator which tells me it isn't part of a post but 'hovers above' it. I'm looking at the ACP header whose large shadow establishes its hierarchy over the particular menus below. I'm looking at the large
reflective 'Register Now' button, a straight copy of key Apple UI elements. I'm looking at 'pressed-in' text (in buttons and elsewhere) having an old typographic feel. See at my default avatar and you'll find a sharp diagonal running through the question mark... what is that? That's the 'sharp glassy reflection' effect Apple has pioneered in most of its graphics since SJ's return.