Stamkos has played his entire 15 seasons with the Tampa Bay Lightning, winning back-to-back Stanley Cups just a few years ago. He was drafted first overall by the Lightning back in 2008. It's obvious he has both professional and personal ties with the City, so it would be hard to imagine him leaving.
However, on the other hand, Boston would be hungry to replace their recently retired leaders in Bergeron and Krejci. Stamkos would be an even better replacement, with a Stanley Cup pedigree and tons of production left in the tank. Despite being 33 years old, Stamkos recorded 84 points last year, and 106 the year before that.
So, while its hard to imagine Stamkos in another jersey, he might just decide to test the market out and see one last time in his career.