AMD's latest roadmap includes a number of interesting changes, but you have to read between the runes to understand them.
A chip codenamed "Newcastle" is labelled as socket 754 and 939, both of which are described as being Athlon64 chips, not Athlon64-FX models. The FX line apparently does not get updated until the 90nm process arrives, gifting us with San Diego. There is a clear differentiation between FX and plain AMD64, and Newcastle is the point of departure.

There is however, a dark side. Winchester, the Newcastle followup, is only a 939 pin product, while the AthlonXP, is listed as 754 only. What this means is that AMD is going to put its socket strategy in the blender, and confuse everybody again.

Read more: The Inquirer.

and to add confusion upon confusion there will be a large and small version of the 939 pin socket as reported here.