The coaching staff will have to see how he fits, but I imagine there's some hope from the front office that he will at least upgrade the 3-tech over Branch with the chance to replace Red if he doesn't play at the 7.5 million level he's owed in 2014.
Williams is a versatile guy and I know Pete has said they see him as a 3-tech, (and I fully agree. I've been saying it since January he's a better version of Branch and can play the same role), but I wouldn't take what Pete says as the full truth. I think they want some competition and insurance at the 5-tech, too.
If you remember the selection of KJ Wright, Pete said they wanted to to "provide depth at MLB" and "we like him at the Mike", but sure enough a couple weeks into training camp we saw KJ taking snaps at SAM, Aaron Curry's position at the time, which imo was the plan the whole time. I could see the same thing with Williams and Red where the idea is to play him at the 3-tech but hope he can grow into the 5-tech role, maybe saving 7 million in the process.