Top41 Im pretty sure this show will go 10 years, and after that anything extra is just a bonus, not many shows run 10 years these days, X Files only went 9, so possibly just L&O & ER, and I honestly wouldn't blame any of the actors for wanting to move on to something new.
I could see it going past 10, but it will depend on how the ratings are after Petersen leaves. If they tank then, yeah, 10 will likely be it for this show.
I really like the sound of this, even though CSI is clearly past it's sell-by-date and I don't want it to wilt away like the "zombie" ER, Simpsons and L&O (who are all grinding on years past their shelf lives). At least bow out like TNG, DS9, and VOY did, but instead around S9/10 (and while The X-Files may have ended before it hit the big ONE-OH, but it was still getting progressively worse and moribund as a series).
I don't think CSI has reached that state yet, though. I'd argue that the seventh season was one of their best, if not their best. Season eight was good as well--the episodes focusing on Warrick were particularly good. Injecting fresh blood into the show--especially via a character with an interesting backstory like Fishburne's seems to have--can really help a show. Nothing lasts forever, but I don't think CSI is done yet. At this point, I'd guestimate a 12 year run. Beyond that, yeah, it might get stale.