You are correct. Belichick knows the answer to the key questions: the situation of Vollmer, Light and Waters. For me, Mankins is a non-issue. He is a key part of our future. Gallery can play in his place for awhile as needed.
TACKLE
We might very well draft yet another OT if Light is retiring. This somewhat depends on how Belichick views the future of Vollmer and Cannon. For me this is somewhat a non-issue. We have Solder at LT, Vollmer at RT and Cannon as the swing OT. Even if this is the case, we might still draft an OT in the 3rd or 4th.
BTW, if Cannon's future is not at OT, we might very well be drafting an OT very early. After all, with Light retiring, what are we to do when Vollmer is out?
CENTER/GUARD
starters: Mankins/Gallery, Connolly, Waters
backup Wendell/MacDonald/Thomas
If we KNEW that Waters were retiring, we might draft an interior lineman by the end of the second round. It is also possible to draft a top C even if Waters is staying. A guard seems out of the picture, unless he could be counted on as the backup center (unlikely). Besides, if Waters were going to retire, I would think that Belichick would simply re-sign Koppen and have Connolly start at OG.
STATING THE OBVIOUS
I don't even want to think of what will happen to posters here if we draft 2 OL's in the first 3 rounds.
I think we need more OL before they're ready.
Gallery is a good insurance policy, but there's no guarantee Waters is coming back. Mankins is a question mark with the ACL injury. Light might retire, which could force Cannon to play tackle. Vollmer may have back problems, on top of it all.
I wouldn't be surprised if they drafted OL with a high pick