From BE website:
The new services will start their daily schedule from Birmingham however will seamlessly link into Flybe’s current Winter schedule from October 25th when the aircraft becomes Isle of Man based, meaning the services will commence from the Isle of Man.
This would suggest another aircraft unless they are dropping current routes. I dont believe the current 3 a/c would be able to accommodate the other routes unless they move say a MAN or LGW onto another based a/c (IE a LGW based or MAN based)