Running through all the QB needy teams and the rumors surrounding those teams i'm not sure there would be such a huge market for Tannehill outside the Titans, yes some teams would be interested but I don't know if there would be a huge scramble.
Just look at some of the QB needy teams and what they have been rumored to be thinking.
Bengals - they are drafting Joe Burrow
Dolphins - rumored to be coveting Tua
Chargers - have been reports over the last 72hrs they absolutely love Justin Hebert (which would be a massive mistake)
Colts - has been heavily reported that Ballard covets Jordan Love
Bucs - if they don't keep Winston reports are they could sign Rivers and draft Eason
Patriots - if they don't keep Brady, Peter King pointed to them looking at Dalton in a trade so they could protect comp picks by not signing big money FA QB
Bears - they have some cap issues to work through, would be creating some major roster holes to fit Tannehill in, also lack draft capital
Raiders - this has been rumored as a possible destination for Brady
Cowboys - would be a surprise if they moved on from Dak
Saints - likely to be Brees or Bridgewater
Panthers - no idea what they do with Newton, has been a lot of speculation that their new owner Tepper wants to make a huge splash in the draft
Broncos - sounds like they are running with Drew Lock
I'm optimistic that Tannehill and the Titans conclude this is the right fit for both parties and can come to a satisfactory conclusion on a long term deal averaging roughly around what the franchise tag would be for 2020, I would be surprised if Tannehill got into the $30 million range on a per year basis, think he ends up somewhere in the $27-29 million range.