I wouldn't bet on any significant UI changes between now and release. If Apple plan to bring Mavericks more in line with the looks of iOS 7, then this is something that they can dedicate to next years release.
One can understand this better by the fact that Game Centre has been left untouched, while the likes of Notes have had a pretty straightforward graphics swap. Afterall, how do you de-Forstallise something like Game Centre whilst providing a suitable stop-gap until OS 10.10? The chances are that the designers focused on the apps that are used more commonly.
Scott Forstall had nothing to do with what has been the type of icons used in OS's for years now. This is in Windows and Linux.
Maybe the crazy over saturated MLP colors is fine for something like iOS, but you can do actual work in OSX.