I hope so, but Apple could lock down the iPhone if they wanted (and it looks like "they want"). I think the likeliest scenario is for the iPhone to require DRM'd AAC ringtones (in the firmware, not in iTunes). In other words, the iPhone itself will only play a ringtone if it has valid DRM; you can upload a non-DRM'd ringtone into the iPhone, but the iPhone won't play it. Doing that would lock out virtually everyone, including people using iToner or iPhoneRingToneMaker.