TBL can't do that. They would definitely not have room for Johnson, Drouin, or Palat next year with Plekanec on the books.

Tampa Bay can't take the cap hit.

Nate is correct. And while Killhorn is nice from the Habs view, do you really want a 40 point guy (now) at 4.45m till he's age 35?

I know that right now they can't take the cap hit, but iif they move other players by the TDL. On a long-term perspective, maybe having plek for one year only might be a good idea for tampa. I heard a week ago that TB and MTL were talking about trades involving plekanec, I just don't see any other scenarios by now.

He's much more than just a point producer.

While that may true, how many 3rd line guys at 4.45m can a team have. He's behind Palat and Drouin in Tampa. And to think he can be a great long term asset (second line) in Montreal, I can't see it. Try fitting him in on Canadians roster with 23 players in 2017/2018. Right now impossible.

TB already has to move other guys at the deadline to fit under the cap next year. This would just make it so that they have to move more guys.
They're in a tough spot because a lot of their big money guys have NTC or NMC. They probably do have to move Killorn, but they must exchange for a "future" (ELC or pick).