There are already indications of rising prices on Semperons. That should have a net positive effect on ASP's since they do seem to sell a lot of Semperons relative to Athlon 64's and Opterons.
Considering the amount of demand for Intel products that seems to be going unmet in 2H05 I would expect that AMD ASP would tend to rise.
The real issue is what happens *next* year when Intel opens the 65 nm floodgates and AMD starts ramping its new fab. I think AMD will be able to withstand this early on better than in the past because of its good, competitive product line in the server and desktop PC segments (although this might be a pyrrhic victory if the mobile sector keeps growing quickly at desktop's expense). But once Conroe starts shipping it could be back to the bad old K5/K6 days for AMD.