“It’s like an era of association with certain roles – a specific part like Spock, or a kind of part, like Sylar — is coming to an end,” said the actor, when asked about similarities between the serial killers he's played on Heroes and American Horror Story. “I think it’s safe to say this will be the last serial killer I’ll be playing for the foreseeable future.”
It could be interesting to see how Abrams and company cope with a loss like Quinto; not only is he a major part of the films, obviously, but also there's the fact that in the past the franchise has always been able to hold onto the actors, with Shatner and Nimoy playing the parts until the studio determined that the pair had aged out of them. The notion of going into a new Star Trek film and having to recast Spock while leaving the rest of the cast in place could be a daunting one indeed.
There is, of course, always the outside possibility that they could bring back Nimoy, if he were willing; as the only character from the original Star Trek universe to make the transition to the rebooted timeline, it seems as though he's in as good a position as any to take on a(n admittedly different) role in helping guide the destiny of the Enterprise.