If all of the WR's perform equally well as WR in camp, the decision on who sticks on the roster in a 5th or 6th spot will come down to versatility. Troy wins that competition hands down because of his value on ST or as a DB.
It's highly likely Jackson isn't in that mix in TC, and with the others already on the roster it makes no sense to push him to be. Therefore he is an excellent candidate to start the season on PUP. So that really leaves it at 6 competing for 5-6 slots (with the 5th or 6th needing to show more than backup WR capability) and Childress/Kight optionally on the PS or shadow roster.
If the 3 guys they picked up this off season as FA WR's all work out, they will pose at least as much of a threat to Caldwell and Gaffney as they would to Troy. While they are younger than Troy, they lack versatility. They are not signed beyond this season and both already make more than veteran minimum.
For the record, while Troy's salary for the last two years has been a veteran minimum one, his bonus in each season ($30K in 2005 and $350K in 2006) did not allow for his salary to be counted against the cap as veteran minimum exemptions. Given our cap position this season I don't think cap hit will be a concern either. It will come down to whether BB believes he can compete for a roster spot. And if he will he likely bumps someone else whose current cap hit covers all or most of his potential cap hit.
I believe any other suitor would be reluctant to sign him for anything other than a veteran minimum deal this season though due to both his age and the fact he's rehabbing an injury. His value to other teams is basically limited to veteran leadership and 4th or 5th WR. Familiarity with the staff, system and teamates allowed him to build value here that he couldn't provide to a new staff, system and teamates due to the time it would take just to assimilate into the offense. So talk of playing elsewhere is just the it's a business dance he a Belioli will do until they get down to talking deal.