Not to early to ask.
Yes, some Tuners are planning engine mods ... I already heard power figures around 500-550 HP for the Cayenne Turbo. There is however a big problem: even with these high power claims, the tuned Cayenne Turbo will not be faster than the stock car. Reason: tires.
I also know one Tuner who plans to hack the air suspension controlling software and offer a suspension upgrade through programming only. Sounds interesting.
Exclusive department is also prepared to offer several options for the Cayenne, maybe a powerkit with around 480 HP. A Multimedia system (rear passengers) with DVD player, etc. is planned too. The rumored Cayenne powerkit also indicates the possible power of an all new Turbo around 2005/2006: at least 500 HP.