Let me put it like this. When we signed Trez, that was the end for Pippo. I'm sure he could have stayed with us as a sub but a player who's been playing regularly for 5 years doesn't want to warm the bench. If a similar scenario was to play out now, it would take a player of Trez' quality - compared to that of Pippo's, to dislodge DP. And I don't think Di Vaio is that player. And that's not about playing the next few games, I mean longterm.
If it was up to me, I would give Di Vaio some time now, since he's doing well. My goal would be to get the best out of every player (at least the players I would consider for the first team) and towards that end, Di Vaio should keep playing. The reason would be that in theory, every player playing as well as possible in the given circumstances, would benefit the team the most. But I just don't see that from Lippi or any coach really. I think most coaches put consistency above all and don't risk benching their proven performers for longer periods. Otherwise Tudor would get a lot more time on the pitch.