Technically, July 1st 2016 is the date when his NTC/NMC/whatever kicks in, so we have until the next offseason to deal him somewhere.
To me, it's an easy choice between him and Vatman.
We haven't even seen Bieksa play for us yet(in games that actually matter).
If Bieksa provides solid defense, and a physical element, I'm not so sure it's an easy choice. You actually have to build a blue line around multiple capabilities. Vatanen helps us with the scoring aspect, but you also need to be able to deal with physical play, and keep the puck out of your net.
Then there is the prospect aspect, with guys like Montour and Theodore. The team may actually be better off trading Vatanen, getting a solid asset in return, and then giving Theodore or Montour a shot. The same could be said of Fowler, if he can't step up. If you move Bieksa and Stoner, you need to replace them. Manson can't take both spots.