When the Bengals signed Jeff Rowe to the team's practice squad, it was really meant as a precaution that if Carson Palmer calls it quits this season; not as an indication; even though Palmer is probably going to miss next week's game against at the Houston Texans. So, it's likely that Palmer isn't going to play the remainder of October, and if he played, he'd return during the final quarter of the season.
On the other hand, there has been some optimism that Palmer could return after the bye week; which would mean missing three additional games -- Steelers, at Houston and against Jacksonville. The Bengals bye week is November 9.
However, from reports that Palmer was surprised by one diagnosis, trying to find any doctor to give him a reason to play this season, and the team declaring Palmer out earlier than the week before, I think it's pretty obvious that Palmer won't play this season.