BOSD... Flybe is due to be 30-40 Captains short by March 2007, due to resignations and aircraft deliveries over the winter. Couple that with the overlap of domestic routes between BACon and Flybe and yes I think it is very plausible that the Q300 could be grounded more or less immediately and all those pilots retrained on the Q400.
As for whoever it was sat in the RHS of the 146 on Fraggle Rock with 3500 hrs. Don't worry you will be straight in the LHS of the Q400. We need Captains and you have more than enough hours for command at Flybe. Commands at present in Flybe are awarded purely on hours, their is no internal waiting list to do it by seniority. Their is not one single F/O left in the company at present with the experience to promote to the LHS, so everyone like you at BACon with about 2500hrs could be looking at immediate promotion, and as said above if the new pay offer gets voted in, £53,500 salary by April 2008!!