Well, we've got two recent rumors, the second one coming from a bit more of a reliable source, that put together seem to indicate that this movie will feature the whole cast of TOS. Given that, the way I figure it is that there are three options: it's going to be set during the time when Kirk commanded the Enterprise, when all those people were his crew (the era of the show). Or, it's going to be set before the show era, with these crewmen either showing up merely as cameos, or the movie will depict them as having worked with Kirk before he commanded the Enterprise. The third option is that these articles aren't correct (or maybe only the Chekov one is correct, and only Chekov has a small cameo), and it's going to be set in earlier years without the ensemble.