1. Joe Reedy reported that the Bengals will not be using their franchise tag this year because it is too costly. The Bengals used this freely in the past to lock up kickers, but apparently see no need to secure a rock solid CB for the $14-$15M it would take, likely, as Reedy points out, because they do not believe that Joseph would sign long term after the Franchise Tag.
2. Joseph's contract expires March 4th, the same day the new CBA expires. If you haven't noticed, not much progress has been made between the Union and the NFL. No substantive negotitions are going to happen until the CBA is signed, and that might be a long time coming, giving Joseph plenty of time to field offers from other teams.
3. Joseph's pricetag for a long term deal just went up to about $10M a year with the Raiders signing of 2-time Pro-Bowl CB Stanford Routt to a 3 year extention worth $31.5M. Routt and Joseph are of similar age and skill, and Joseph can likely command this size deal on the open market. The Bengals are not likely to want to invest that kind of money.
So come next season, you can expect to see Carson behind center but it is becoming more and more likely that Joseph will not be in a Bengals uniform.