This makes me sad. :(
Nine was my first Doctor. He was actually my introduction to Doctor Who in the first place. While we know nothing on what the anniversary episode will contain, and perhaps it was about the direction or that what they were planning on doing just didn't fit, it's still rather disappointing all the same. Especially since Nine is so under-appreciated and overlooked by most in fandom, I would've loved to have seen him make at least a brief reappearance even if just to be all, hey, he existed too, y'know.