And Chupacabra, I wasn't saying Shatner simply shouldn't have taken the role because it reduced his chances of being in future Star Trek movies. I was saying this was one of the reprecussions of him taking on the role, but the real reason he should have turned it down was simply because it was written in a way that used his character poorly.
I guess he thought he was signing up for something that used his character the way the new movie used Spock - as a figure that is integral to the plot and with reverence for the character's importance in the history of the franchise. Yes, he was written as heroic and an important catalyst for the heroes to solve the central conflict, but his ultimate fate was bunk. He should have rejected the offer as soon as he read the part in the script about the ridiculous fist fight on the rickety bridge.
Remember - Shatner lived in a pickup truck camper for a few years after TOS went of the air; and in 1994 TNG was at the height of it's mainstream popularity, and Paramount was basically telling everyone "Here's the new Star Trek movie franchise..."
Given all that, I fail to see why Shatner (or his agent) would think: "Hey, let's pass on a 12 million dollar paycheck just in case the TNG franchise falls flat and they decide to bring the original cast back again in some form..."
As for Nimoy, I do think he's a good guy, but even back in the days of TOS; there are stories of him going overboard on maintaining 'the integrity' of his character and the show; and there's even one pretty famous memo where the NBC heads are writing GR saying essentially "We could understand these demands if this were a top 10 show, but is Nimoy aware of the ratings?"
This is no denegration of Mr. Nimoy per se as he's now financially well off enough to do whatever he wants; and has plenty of other interests outside of acting to occupy his time.
Mr. Shatner on the other hand seems to be one of those actors who only really enjoys acting; and also comes from and has experienced 'starving actor syndrome' to the point where he goes with the old addage of 'never turn down a job with a good paycheck."
So, again, I will never understand why people look at him funny for accepting a 12 million dollar gig. He understands what many fans don't - Kirk is a FICTIONAL character. Would he have loved to see a part for the original Kirk in the new Star Trek film? Yes - but only because it would have netterd him another large paycheck; not because he cares about the 'integrity' of Kirk. Hell, he pictched a Kirk story to the producers of ENT; and didn't turn it down because of what they wanted Kirk to do in the story; but rather because they couldn't meet his asking price.
