I acknowledge Trezeguet as one of the best, if not the best, foreign players Juventus has had. However, the way I see it is that his ass is probably around 80% out of Turin after this season, and Juventus needs to fill that gap with a fairly tall striker with a lethal finish.
Personally, I think this Luca Toni stuff is complete and utter bullshit. I don't think he would be very reliable even if these biased Tuttosport rumours were true. Klose, on the other hand, is probably the closest Juventus can get to a Trez clone. You may not care about how he adds more to the game overall, but in the end it adds balance to that front line, which can produce plenty of goals. Klose shares the same aerially supremacy as Trezeguet, probably can't place/finish as well as Trez (but nonetheless does it well), but he can definitely dribble better.
In the end, it balances out; where one lacks, one makes up for in something else.