Wouldn’t he have to sign the tender before being traded? And if he’s being traded to some **** team, why would he sign it?
No. He can be traded without signing the tender and the team trading for him can pay him more than the franchise tag amount on a one year deal, but a long-term deal cannot officially be signed until after this season.
If the Steelers let him walk in the off-season they'll get a third round compensatory pick. I don’t know what trading his fatass for what’s left of the 2018 season with no guarantee that he’ll re-sign with that team would net in return, but at least the headache will be gone.
Regardless of all that, I could see a team like the 49ers (McKinnon signed long term but out for season, currently wasting the first full year of the Jimmy G era) be interested in Bell’s services for this season and then allow him to hit free agency in 2019.