It's a bummer about Eccelston. I kept hoping he'd have that last minute change of heart. The first time I saw "The Five Doctors" in the 80's, I was pretty bummed that Baker wasn't in it. (This was before I'd seen any 1-3 stories, so I was only really familiar with 4) A lack of Eccelston gives this special that same vibe for me. I'm sure I'll enjoy it, but I notice his absence.
If 9 won't be there, I would like them to try to get 8 in there, simply because I'd like him to have another moment on the screen as the Doctor.