I would have liked to see an annual Trek film with the original cast before any of the actors beamed up to the big Enterprise in the sky, but the company didn't know how to handle the lightning in a bottle Star Trek was ... and is.
Six original cast films seems enough to me - as they pointed out in TUC they were all getting very old, too old to be believable as active personnel.
It is hard to make a new film in a franchise annually. Apart from anything else it takes pretty much a year to actually make a film, let alone distribute and release it effectively. That and the lack of "event" associated with the films would pretty much guarantee a series of flops.