I don't have any concrete info, but I've heard that Intel is releasing the Pent. 4 **1.9GHz** very shortly. I'd imagine that as Intel phases out Pent III, AMD will accept the fact that they need some higher clock rates to compete with a Pent 1.9GHz that sells for less than $300. The 1.8GHz is 'sposed to drop to $260 or so later this month.
Just guessing, but I'd say we should see an Athlon 1.5 and 1.6GHz here in the next 3 months. However, what I don't know, is what max speed their .18um technology can support. It is likely that the faster chips will be .13um, possibly with copper interconnect. Again... this is all just speculation on my part.