Your projection is probably close. Though I believe this passing offense is going to be solid now and into the future. Finding enough balls to go around might be the problem.
I think the Skins have done a nice job of easing the eventual transition from Brunell to Campbell. Unlike most rookie (or first-time) starters, he'll be going into a decent offense with plenty of weapons (Portis and the receivers).
The flip side to that coin, is that Washington has plenty of room to grow offensively... at least passing wise.13th in points scored
22nd in passing attempts
22nd in passing yards
It's not like they are topping out top 10 in every category. Of course, in order for Moss/Cooley to retain most of their stats from last year and have Lloyd get respectable #2 numbers, would mean Washington becomes a top 10 team in terms of passing yards. Probably not easy to swallow for most people, but it's certainly a possibility.