They'd be stupid to ever end it. Its like a top 5 series, hell maybe top 3 with COD and Halo...didn't expect it to be announced so soon tho.
I figure they will go the Star Wars route...give u the original trilogy, then a prequel trilogy...after that then they can even come up with more story to pick up after Gears 3(haven't read the books so i guess it might even be plenty left there to cover as well).
Definite first day cop for me...i need to get on completing some Gears achievements!!