I think 6 is very reasonable. We have been able to carry 6 in the past with no issues, although 5 is more common.
We still do not know if the philosophy has shifted and we will be more dependant on the pass this year. If so, having 6 good WRs is a bonus, but not a luxury. We will have injuries to the WR corps. We will use 4 WRs sets in every game. 5 would be active, and the 6th active whenever there is an injury.
The other side of the coin is that Watson can be considered the 5th WR, Faulk has at times filled in there, so only having 4 active with the 5th ready for injuires is doable too.
Its a great problem to have.
IMO, after Moss, Stallworth and welker who are all arguably better than any WR we had last year, we have last years #1, a guy who came in and became very productive by the playoffs (Gaffney) a guy who seems further ahead today than Gaffney was when he joined the team--as well as more physically talented (Washington) plu Troy Brown, and last years 2nd round pick probably going to pup.
Washington is the wild card to me. We havent seen enough of him to judge, but through a full camp, I guarantee BB has determined whether washington is a guy ready to tap his immense potential (he would have easily been a round 1 pick if he wasnt injured) or a guy who will just never reach that level for whatever reason.
To me he is a roster decision in a vaccuum, regardless of anyone else. If BB sees him capable of reaching the potential (and close to it) hes a lock. If he is just struggling to fill the last roster spot he can stay or go, no difference.