Nah. I don't believe that for one second.
You have a few things wrong here:
1) There is no material benefit to the Tigers whatsoever getting him off their books. They have to pay him what they owe him. End of story. And they're not even in the ballpark with regards to luxury tax... they're on the beach soaking up the sun... no taxes whatsoever.
2) The only benefit to getting him off the roster is competitive. If he's turning into a black hole in the lineup - and he did keep his head above water this year... eventually... it took him awhile to get to acceptable numbers - then it benefits the Tigers to just pay him his money and wave him off into the sunset and get an actual contributing bat on the roster. Now... there are political issues involved here between Miggy, the Tigers, and Fans Goodwill... but if it's pure competitive, then the Tigers' need to wave goodbye to Miggy some time in 2022... after he hits milestones.
3) He's not retiring. He's not forfeiting anything. And the Tigers won't pay more than the existing contract obligation to say goodbye.
I'm not certain about player development in Lakeland... maybe... He might be down with that.
But if the Tigers make a serious playoff push... I think he would absolutely want to be around the team, as bench coach or otherwise...