there will be an option for ringtones in the very near future. during steve jobs demo of the iPhone, there was a ringtone tab in iTunes. Additionally, in the iTunes 7.3 package, it contains a ringtone.gif image. I would give it about 2 weeks.
I am sure Apple is just trying to work out a deal with cingular so we don't actually have to buy the ringtones and we can just use songs from our iTunes.