Question is...do you really want a socket754 system? It seems to me that AMD's x86-64 strategy is really going to lead to some confusion. We'll have socket940, socket939, socket754...
Or, as the guys over at overclockers.com say, you'll have the Opteron (socket 940), the Athlon64 FX (initially socket940 but later switching to socket939), Athlon64 (socket 754, single channel memory), Athlon64 That Isn't An Athlon64 (socket754, single channel memory, 256KB cache, x86-64 circuitry disabled, branded as "AthlonXP" though it's based on the Athlon64 core, not the AthlonXP core)...
Methinks it's going to get complicated