I would think you want good blocking WRs to make the read option work. Obviously they still need to catch, but look at Pittsburgh in the early 2000s, they were known for having the best run blockign WRs in the game. THey could still play receiver just fine, guys like Burress and Randle El. The scheme will depend on good downfield blocking to give the QB or RB a chance to make a play. Sometimes if a TE or slot receiver doesn't get a block on a Safety, the Safety could blow a play up in the backfield if he's comitting to the run.
Depending on the answer what does this mean for the WR position? Is it going to be as important to teams that draft the read option QB's to have great depth at the WR position? If a team does have great depth, will the players all be getting the chances to get the numbers they want in order to get a bigger contract when theirs is up? Do the 2nd and 3rd WR's need to be better blockers than WR's in order to be able to block more down field and give the primary guys better chances at making extra yards?