I'm going to stay away from the "Jets will be in cap hell" argument as it does seem to be said every year, and every year it works out. I do think the challenges are mounting however. In 2013, they will likely have to cut Hunter, Pace, and Scott saving about $19.5 million. Of course, they then have to replace those players.
I believe the following are the free agents come 2013 who will need to be-signed or replaced:
And you also have Revis lurking out there looking for another huge payday.
So is it cap hell? No. But it could be challenging and is definitely a result of pushing money into the future. As others have noted, I think Tanny (and many others) expected the cap to increase year after year. No one realized (at least on the player side) that the league would have to artificially borrow for future years to shore up the cap so it wouldn't decrease.