i dunno, i'm not so sure. the ratings aren't as good as last season, sure, but everyone knew they'd drop moving to fridays. and i read somewhere that the drop between ep 1 and ep 4 is less than the drop between ep 1 and ep 2 last season so i think there's still something there.
that said... and don't get me wrong, obviously i'm a big fan of the show and whatnot - i kinda hope they do cancel after this season. i would much rather it quit while it was ahead (just about) than go out limping (in fact by about half way through last season i was actively hoping it would be cancelled because last season was so goddamn shit - but this season so far has been better, thanks to the creative oomph they've all got by hiring sela, so my enthusiasm is back, at least a bit). also i think with gary so busy elsewhere it could be a possibility. personally i'd rather see him doing something else than csi - much as i enjoy csi.
so y'know, i actually think it's less likely than people make out but if it happens, meh, i'm cool with that.