It's maybe a bit early, but it's always nice to discuss at least the current prospect of overclocking Athlon 4. Basically, Athlon 4 comes with the already known bridges that determine the voltage and multiplier. There are quite a few more bridges on Athlon 4 than on Thunderbird however. It is certainly not going to take too long until the meanings of those bridges will be revealed to us.
Due to the PowerNow!-feature of Athlon 4, there might be a new and much easier way to overclock Athlon 4. The power-saving feature allows the adjustment of the core clock on the fly. It might well be the case that the multiplier can be altered to higher levels than the specified clock speed. Maybe all it takes is just a hack of the PowerNow!-software.
The multiplier settings of Athlon 4 have changed a bit, as they now allow multiplier settings of up to 18x. Here are the new specs: