Unfortunately 939 is a considerable price jump, especially for the CPU. Even the motherboards are more. The 939 is a better choice, but not sure the price jump would be justified.
So far in all the years I have been building computers I have only managed to re-use a motherboard once, and this was really only becuase I got a killer deal (So good I actually upgraded from a 1.2 to 1.3 Athlon, small jump, but like I said good deal). Every other upgrade has always included a new motherboard, generally there is always some new feature out that I want, or have to buy a new one for a faster FSB, etc.
Nothing is certain, by the time he wants to upgrade, who says 939 will still be out. So far it seems AMD will be sticking to it, but that could always change.
My Desktop: <A HREF="http://Mr5oh.tripod.com/pc.html" target="_new">http://Mr5oh.tripod.com/pc.html</A>