I still think it's a bit too soon to give up on Brohm.
Rodgers has been injured before, and Flynn took an injury just tonight. It would be foolish to retain only 2 QBs on the roster, so the argument that we can save a roster spot for another player doesn't apply without someone like Favre or Manning.
The next question is whether we should replace Brohm with another veteran. I don't think this is particularly a good idea either; if we sign a certain #2 (say, Tarvaris Jackson) then we stunt Matt Flynn's continual growth. If we sign a certain #3, then we may as well keep our chances alive with Brohm improving this season and the next offseason.