It'd be a shame if they didn't bring it back to Boston. Chicago would make a great FF host city given its central location and accessibility, and abundance of sightseeing, lodging and food/drink establishments. Ditto w/ going back to D.C.
Brooklyn is an intriguing option simply b/c it's NYC, although it remains to be seen how the sightlines are once Barclays Center is configured for hockey upon the Islanders' move.
Boston, Chicago, D.C. and St. Paul would be my choices. Anywhere but Columbus.