That would still be 1.5+21+21 with the signing bonus making next year feel better than that 1.5 for him. You've still not come to terms with 'extension'. He's likely asking for the larger bonus and guarantee to compensate for next years salary
No, any contract that is renegotiated by Wilson and his agent will have him getting substantially more THIS year (2015-2016), so your 1.5 + 21 + 21 example is wrong. The only way Wilson makes 1.5 mil this season is if Seattle chooses not to renegotiate (which they can do). If they go this route several things can happen:
1) Wilson sucks it up and plays for 1.5 mil. In 2016-17 he becomes an unrestricted free agent. If he so chooses, he can refuse to negotiate with Seattle, forcing Seattle to either Franchise tag him or let him walk away. If Seattle chooses to franchise him he will play for one year at roughly 22-25 mil.
2) Wilson refuses to play and holds out. He can do this, but what he loses is his ability to become an unrestricted free agent in 2016-17. However, he can still become a restricted free agent and test the contract waters in 2016-17, but Seattle has the right of first refusal, and can match any offer sheet made by a new team.
3) Wilson can walk away from football altogether and play baseball. I have no idea if this is a real threat and what the level of interest for Wilson would be in the MLB, but if he went that route he is not bound by anything contractually with the NFL.
There is no way that he renegotiates his deal but remains at 1.5 mil this year. Signing bonus's are a part of Salary