Given Canonical's history, it's not hard to imagine them jumping from "we're thinking about it" to "we're doing it" prematurely (like they did with Unity, regardless of weather you like it or not). Even brilliant engineers are only capable of so-much work per-person. If Ubuntu had chosen Gnome (or forked it like Mint/Elementary), then that would be receiving a lot more attention now, and be a lot more developed today. I like both Gnome and Unity, and I have complaints about both. But it's funny to me now, that with only a few extensions Gnome can behave very similarly to Unity.
Keep in mind one thing however: Canonical employ intelligent and capable engineers. One expects that whatever decision they take, they'll have some fairly good reasons for it.
( anticipating moans about them dropping Gnome shell for Unity, answer this question honestly - knowing their goal was to build the Unity experience, do you honestly think they could have done it while also aligning development with Gnome shell? (whether you like Unity or not is irrelevant) )