Maybe, but the fact that CE did meet with SM, SM had to show him a script or an outline of the story. So a story with a third doctor did exist (Let's face it, we always new #10 would be in the 50th no matter what). Since CE again has disappointed Dr Who fans (notice I said Dr Who fans, not CE fans), the story with 9 included may be able to be changed with minimal effort to include 8. UNLESS the story heavily involved all three of the doctors knowing Rose and Rose knowing 9 & 10.
The original plan 'could' have been to have 9 and Rose and not 10 since he just recently left the show. When CE declined the offer, then they changed it to 10 and Rose.