The right side of the line is set and won't change in 2013 without injury.
RG- Josh Sitton
RT- Bryan Bulaga
Bulaga and Marshall Newhouse are Tackles, not Guards and that won't change either. Newhouse is a serviceable Tackle as a backup, not a starter.
I'm fairly confident that T.J. Lang won't play a position other than Guard as a full time starter.
I'm thinking three positions are locks, LG, RG and RT with those mentioned in the earlier post.
LT- Derek Sherrod, that's more of a hope that he proves to be good enough at that position. He is a Tackle, not a Guard as he proved during his rookie season.
C- I haven't a clue if Evan Diedrich-Smith is the answer or believe to be.
I do know that when your QB takes more sacks than any other in the NFL, even with him holding the ball too long ... the OL needs to improve on pass protection.