The chairmans statement from November indicates 60 Q400's when the EMB145 substitution programme is completed in 2009, plus 5 more firm orders for growth, making 65 in total.
http://www.flybe.com/pdf/chairmans_statement2.pdf
I'm sure there are more options out there too, but I can't find any mention of these. Jethro's UK airline fleets shows 15 options.