I would stand pat. I'm probably in the minority, but I am not sold on Johnson being a long term staple at RB. I would hang on to Jackson and hope he can stay healthy for a season because if he does, he's a top 5 pick next year. I think you'll be ok at QB, Cutler might not be great this year but he should be back to form by next year.
Is that this years rookie pick? If it is, I would try to land James Davis with it to back up Lewis. You should be set at RB then for awhile.
"Maurice Jones-Drew, below the waist, is incredible." Mike Mayock
If this were a regular league, I wouldnt do it, but in a dynasty league I would seriously consider this. CJ4.2 is a bit of question mark for me, the sophomore slump for RBs is always looming until proven otherwise, but having White will help preserve him for some seasons to come. Also, the potential of VY to start next season is a plus. Palmer is my comeback candidate of the year. He cant do any worse than he did last season and he's still a good young QB with plenty left in the tank and rejuvinated Ochocinco.
S Jax is in a poor offense and a injury risk, but still a good RB. In a dynasty league, I would want Palmer over Roethlisberger.
I would lean towards making the trade, but it's close. Carson is more valuable than Roeth, but Johnson / Jackson is close. Jackson is they only guy in Stl while Johnson will lose TD's in Tenn. I'd guess next year their draft slots would be close, and then after that, who really knows. So to me, the decision is how much of an upgrade is Palmer over Cutler, and is it worth losing your rookie pick. If you don't think the rookie is worth anything, go for it. If the rookie could be a valuable keeper, I wouldn't do the trade.
Not really sure of the value of that rookie pick (who's available around 2.2?), but for the guys playing now, I would do it. I like Palmer a lot more than Roethlisberger, and while I like Jackson a little more than Johnson, the difference is not huge and Jackson is a much bigger injury risk. Plus Johnson is younger (although Jackson really isn't very old -- just turned 26), so that's a little boost.