i think right now Giovinco is the direct replacement for Nedved. Del Piero has another season left in him as a starting player.
I believe eventually Giovinco will move into the playmaker role behind the forwards (where i think he would play his best, alla Nedved under Lippi) or probably play the role like Messi does, but on the left (which in this case would be similar to Del Piero's role over the years). This will happen when he gets more experience at the highest levels in the CL, but playing him on the left now is a good way of developing and implementing him into the first team.
It all depends on what Ranieri's plans are for next year in terms of formations and tactics. Right now, denting any chances for giovinco to play would be ludicrus.
As for De Ceglie, as he develops his defensive and offensive skills more, he'll offer good service on that left. Pessotto was no Roberto Carlos when it came to attacking, but he did his job well for many years and played an integral part on the left through those winning years for the club. De Ceglie can be the same, if not better.