I was thinking about this very topic last night, good thread.
Usually from past teams, we keep 5 WRs. However, I wouldn't be suprised to see Saban keep 6 this year just because of the quality players we have for depth. This is what I see:
WR1: Chris Chambers
WR2: Marty Booker
WR3: David Boston
WR4: Derrius Thompson
WR5: Wes Welker
WR6: Bryan Gilmore(If we keep 6 he stays, otherwise he gets cut)
They seem to be trying to include Wes in the passing game more then just having him as a Kick/Punt Returner. It will be very interesting to see what happens.