Being at the office right now, I don't have access to the sites where the announcements were made, but with the stories that start airing in 2013, Character Options will switch to the smaller 3.75 inch type figures (Star Wars scale).
Source is an interview with Character Options Brand Manager Mark Hunt from the Doctor Who Supplement of Toys 'n Playthings
. You can read the interview here
, on page 14.
I'm disappointed about the scale change, but now that I think about it I was probably done getting nuWho stuff anyway. I'm really glad though that the Classic figures will remain the same size.