As much as I like Portis, I think he is near the end of his career. He doesn't practice any more, and he just doesn't seem to have much desire to play anymore.
I do agree (though you didn't say it exactly, just alluded to it) that in the NFL a team needs two feature backs. Though perhaps not the future star running back for the Skins, Quinton Ganther has looked quite impressive while filling in for both Portis and Betts. I don't know much about Gerhart, but if you compared him to Riggins Gerhart could be the power back while Ganther is the speedy back.
Perhaps Campbell will be given one more chance next season. With that said I feel Campbell was given his chance with the Skins and it won't surprise me if he isn't with Washington next season. I'm still hoping Brennan is given a few shots to start next year. He was a Heisman candidate a few years ago who the Skins drafted in the 6th round. Perhaps he'll amount to nothing, but perhaps he'll end up like Brady (a low draft pick who adjusted to the professional game quite well).
All I know is Bruce Allen has a lot on his plate this coming off season, lol.