I'd give a 4th for Campbell. If they do, count on both Johnson and Griese being cut. Campbell will be the starter with Leftwich and McCown vying for the backup duties.
I think I'd still be ok with that. JJ hasen't shown anything great and seems undersized to begin with, and BG...well, he's BG. But I think they would let the three sling it out for the spot. They kind-of HAVE to do SOMETHING with McCown (after all that talk they did) imo.