SteelBuckeye posted a nice link to this in the other brown Hold out thread. And according to his link the trade scenarior is not ruled out by the cap if draft Picks are involved. I will copy my reply below.
Steel Buckeye great link. If those guys have it figured out correctly in the table they provide
2015 $6,000,000 $3,787,500 $0 $0 $0 $9,787,500 $9,662,500 $125,000
2016 $8,250,000 $3,787,500 $0 $0 $0 $12,037,500 $5,875,000 $6,162,500
2017 $8,710,000 $2,087,500 $0 $0 $0 $10,797,500 $2,087,500 $8,710,000
This is for a trade or a cut showing the salary cap implications. The third column from the right shows what his hit is for this year and the rest of his contract if he honors it. The next column to the right shows his hit if traded and the far right shows cap savings. So in looking at this list it appears the prorated money or dead money. There was a little box that deals with the different trade or cut options by year and before June 1st. So if traded or cut this year or any later year there is in fact a net cap savings.
Draft picks are fairly inexpensive to sign and the steelers would be enough under the cap to sign a second first round pick this year. It does not look like the salary cap will limit them regarding the trade option. The big question regarding the cap would be how his new demands affect it and what kind of a message that sends to the other members of the team. Not saying how good AB is or his worth at this point but do you really want the players demands to be managing your cap as giving in at this point sends the wrong message to the rest of the team. I suspect there are lots of players that feel they are under paid at this point. For example what are we paying Beachum, granted he is not a premier left tackle but he is our left tackle and I would not be surprised if he is not being paid way below starting tackle money for example.
The thing with considering options is just that consider them and decide based on what will be best for the team and not a fan that thinks the world will end if a player is traded. Lots of folks thought the world would end when Wallace left but it kept on spinning just the same.