I'll be severely peeved if no one from before 2005 appears in the special. I'm quite frankly appalled whenever I hear anyone saying that Ten, Rose, Zygons and UNIT is good enough.
As a practical matter, there's unlikely to be much, if anything, pre-2005 in the anniversary special. It's a problem of budget. The anniversary special is 75 minutes and in 3-D, all made (per Moffat) on the budget for a standard length episode. Simply due to the budget, it's unlikely there will be many guest stars. (I suspect River Song is the most likely unannounced guest star.)
To be honest, because of the budget and the need to stretch it to the breaking point, I'm expecting something on the scale of "Waters of Mars" -- a couple of sets and a small cast, essentially a bottle episode.