Right now the Steelers cap hits for AB the next 3 years are $22, $18, and $19.5 million. If we trade him this season, that changes to a dead cap hit of $21 million with $0 in 2020 and 2021. If AB retires, I believe there is still $12 million of his prorated signing bonus that applies to 2019, 2020 and 2021, so he would have to pay that back if the Steelers fight him on it. So if he retires we lose any possible trade compensation, but would gain $12 million in cap space over the next 3 years. I would definitely rather have a pick.
I think two main possibilities are AB plays for the Steelers, or gets traded, I don't think retirement is on the table because I think the Steelers would balk first and trade him for less to somewhere he thinks is worthy of him.
Also, hopefully by now the Steelers have a list of "acceptable" locations if they're going to allow him to dictate trade terms.