I'm actually surprised that they released Luton. That leaves them with just 3 (Carr, Winston, Haener) to go through training camp. Maybe they plan to pick someone else up to ease the TC load.
Yes, I know some will think, "but what about Hill!?!" Hill may be an emergency QB during the season, but teams typically carry that 4th QB in TC to lessen the load on their better QBs just during TC then release that QB (or place on PS) prior to the season. Hill will be too busy working in his myriad positions.
Luton would have been perfect in the TC role.