The Office has been one of our favorite shows since it began, and I'd hate to see it go as well. At the same time, although there have been some funny moments this season, it doesn't seem to be quite up to the levels of the last few seasons. I think if Carrell indeed was leaving after next year, it would be a good time to just wrap the show up. They, of course, probably won't do that and the show won't be nearly as good because of it. There are a lot of shows these days that although I still watch them and enjoy them, I'd sort of like to see them end "on a high note".
This happened last year with the show Scrubs. I don't know if anyone watches/watched, but they had a great finale that was designed as a "series finale", but then ABC picked up the show so they ran a sort of "spin off" with a couple of the same cast but mostly new characters (and the same name). It was mildly amusing, but just not "Scrubs" to me. Anyways, on a more positive note, if anyone is looking for a good comedy to check out - give a watch to Modern Family on ABC (Wednesday nights). Probably one of the funniest shows on TV right now I think.