If the iPod Touch ever gets a 3G upgrade, I can easily see Apple doing some hard-coding into the system in order to prevent hacks like PhoneItiPad, or somehow preventing you from using it as an iPhone substitute. As for the VOIP applications, you would be forced either to use earbuds or the speaker to listen to phone calls, and I think it's enough of a reason for most people to still get the iPhone, or using the dumbphone + iPod combination, like now. And the 3G addon will cost 100-120$ most certainly, so they will still make a major profit out of it.