I think this is a good thing in the long run. I have no problem being the beta tester for a unifying ui. This can consolidate development focus which arguably will reduce bugs. As people get more tired of one ui, there will likely eventually be enough pushback to cause more custom options.

A major difference between ubuntu and every other os is ubuntu is open source with a rich enough history to show it has staying power. Worse comes to worse another fork happens. But the OS UX paradigm has a huge opportunity to evolve with this kind of focus