Nope, that's what the extra pins on 939 are there for. I wouldn't worry about it... the dual-channel CPUs will perform higher at at given clockspeed (other factors being equal) but AMD will be accounting for that in their performance-rating number and charging accordingly.
edit: to be more relevant, the roadmaps show that AMD will be using the dual memory controllers to offset the performance drop of their general move towards smaller cores with only 512k of cache instead of 1MB.