They're moving to Montreal, but they can't move with that lease right now so they have to float this idea in the interim. Plus, they want to make sure Montreal can get them a new ballpark and this gives MTL time to build it for them, and then they'll be gone for good in 2029 or earlier if they can negotiate out of that iron clad lease they've got down there. St. Pete is hilarious, they're sticking to it really hard without realizing or caring much about the fact that the team will surely be gone by the time that lease ends. Not that I blame them for not budging on building a new ballpark.