I read the "We're talking, we're talking" interview. I suspect, with only a little over a year to go before hitting the big screens, that there will be a bazillion rumours floating around. IF, they decide to put Spock prime into this film I sure hope it is more for just window dressing. Knowing Nimoy, though, I suspect that is exactly what they are 'talking' about.
I always thought Nimoy wouldn't do a window dressing style cameo. He dropped out of Star Trek: Generations because that is all his appearance would have been.
Who knows? Maybe he has changed his mind about that sort of thing?