The Bills won't let Glenn walk if Henderson and Kujo clearly aren't able to man the tackle positions. But, say they both show up big in TC/preseason and we end up having perfectly good starters in both of them, the scenario where we lose Glenn becomes more likely and reasonable. Gilmore and Dareus will command big $. Can't keep all of the players always.
Then again, if Glenn is back on track to being dominant at LT, well then I'm sure we will do our best to keep him, knowing we have good OT depth.