That leaves OL, WR, and CB as the team's biggest needs. IMHO, they will take the best player available at one of those 3 positions.
As much as I would like him on the team, there is no way the Saints let Nicks go... He is an absolute stud...and young too.
Also, I doubt the Niners would invest that much money in an OG to be frank, especially since they have a lot of good players to retain in the next couple of years. I doubt they sign any really high profile FAs actually, unless they think one player could put them over the top.