The Bengals showed why you want 2 good WRs. I like Antonio Brown, but he is no AJ Green, and Green was taken out of the game by the Steelers. Much harder to 2 when you have to worry about 2 WRs.
I would like to see Wallace return (at a reasonable rate, of course) because of the balance he brings to the offense. Even with a few drops, you have to account for his speed. If a deal cannot be reached, the Steelers need to get value in return for Wallace. Otherwise, it would open a big hole that needs to get filled.
I still don't think the Steelers should pay him 50million or more and I don't see them doing so.
If Sanders stays healthy, I think him and Brown will be top 2 receivers next year. We'll see if a 2nd year guy, an upcoming draft pick or Cotchery will be our #3.