He should keep in mind that Juve gave him the chance to shine on the big stage, twice, both as a player and as a coach. The club also stood by him during Calcioscommesse. I don't expect him to stay on forever like Ferguson at United, don't get me wrong, but I would be really disappointed in him if he didn't at least stay for 2-3 more seasons.
If Juve wouldn't offer him good enough wages, it would be understandable if he left, of course. But I think Juve would pay him what he deserves, and then some, to make him stay. If he was to leave despite of that, I'd be very disappointed.