Selling Thuram would not be a good decision IMO. Although he's 32, he still has pace - it's not as if he will lose it overnight just because he's over 30.
Thuram would probably have more pace than Montero, Iuliano etc when he's 50, so why not play him till then? After all, we still play Montero for some unknown reason.
Whatever you say about our defence, Thuram is quality. If we are getting all these new defenders this summer (as everyone seems to think) - surely we need someone in there who has experience and can help bed the others in.
All the names that are being banded around (Ferrari, Bonera, Mexes etc) may have potential, but all are unproven at the highest level - i.e CL. We need to keep some of what we already have.
If we sell Thuram it will mean another season of Montero - I couldn't take it. I'd keep Thuram and Ferrara (along with Legro). Juve should look for a good right back and put Thuram in the middle, but he's great on the right either way.