As a Lightning fan I'd make this move. I'd even throw in a first if necessary to sweeten the pot. I don't see Yak making our roster but with the net $2.5M in salary going out the door plus the $900k for burying Yak in the AHL we'll be able to resign Kucherov this summer, and Yak's contract expires after this season so he won't screw up our plans for the future.
As far as retaining on Filppula goes (instead of adding a pick), I'm less inclined to do that. Ideally I'd prefer to package Filppula with a first and/or prospect to a team that would take him off our books entirely. That would then allow us to buy out Callahan which in turn gives us at least a chance of keeping our entire top six intact going forward. Retaining on Filppula to move him now, while it would help us sign Kucherov this summer without having to trade a more valuable player, kills our chances of getting out from under his contract entirely. Plus the more we retain on Filppula the better his value becomes, and in that event I would want somebody useful coming Tampa's way rather than Yak.
So basically moving Filppula's contract in full is worth a first and taking on Yak to me, but retaining is probably a no-go unless Edmonton sends us somebody better than Yak.