My 2 cents, 5 for 50 with 30 guaranteed. . .take it or leave it. However, he should be franchised so the Steelers have some protection throughout this negotiation process.
As a 3rd WR, Sanders will be lucky to see 4 for 16, but IMHO, I think Sanders wants to be a #1 or #2 so I doubt it highly that he stays in Pittsburgh unless they tender him like they did Wallace this past season.