He would be worth a first round pick if you could have him for four years, as with a draft pick. Or if there was any chance at all that he won't just be a free agent. Right now all the third-round picks gets you is something you might be able to have for nothing, and under a long-term contract to boot. The only reason to give that up is if you don't think you are a team he would sign with on the open market, and if that's true do you really want to give up a draft pick and $25 million to try and change his mind?
If if it's really true that his value is even higher now than it was a week ago he has no reason to pass up the open market. If he is franchised and traded can that contract even be renegotiated or is he locked into the terms of the franchise tag until next year?