From Hoopshype...
Player 2006/07 2007/08 2008/09 2009/10 2010/11
Shawn Marion $15,070,000 $16,440,000 $17,180,000 $0 $0
Amare Stoudemire $12,000,000 $13,260,000 $14,520,000 $15,780,000 $17,040,000
Steve Nash $10,500,000 $11,375,000 $12,250,000 $13,125,000 $0
Kurt Thomas $7,355,625 $8,091,187 $0 $0 $0
Raja Bell $4,500,000 $4,750,000 $5,000,000 $5,250,000 $0
James Jones $2,652,000 $2,904,000 $3,156,000 $0 $0
Howard Eisley $2,200,000 $0 $0 $0 $0
Boris Diaw $1,795,757 $2,587,685 $0 $0 $0
Leandrinho Barbosa $1,679,733 $2,502,802 $0 $0 $0
Pat Burke $810,000 $0 $0 $0 $0
TOTALS: $59,373,115 $56,820,187 $52,106,000 $21,030,000 $17,040,000
None of those totals are over the expected $62 million. We technically are not over the cap in any of these years.
In 08-09, if we keep all of our players (meaning the ones that we have signed, Marion, Amare, Nash, Bell, and Jones, we will be around $52 mil. If we signed near miminum contracts for the rest of our roster, we would not be in the luxury tax. Yes, this is unlikely, but given some of the views of Sarver on this board, it isn't that far-fetched.
Yes, trading Marion is likely to happen after next year. In your scenerio, Wilcox would take up about half of the savings that we would have by trading Marion. What do we do with Diaw? The amount that is left, will either barely cover, or will not be enough to resign him. Barbosa would have to be a walk as well.
This is assuming that Sarver would not go over the luxury tax.
Overall, I think that a S&T for Wilcox is not a good idea, because it hinders or may even prevent resigning Diaw.