In a bit of slightly disparaging news, it seems that 939 is dying out sooner than expected. AMD does not plan to release the FX-62 or the X2 5000+ for the 939 format, instead making them AM2 offerings only, despite information to the contrary in the months past. The pricing information and spec information for these CPUs has also been removed for socket 939 on AMD's page, so in all likelyhood it may be that the 4800+ and the FX-60 may be the end of the line. For a long time, people lauded AMD for their long continued support for Socket 462, which lasted longer than any other CPU socket has, with a wider range of processors than other sockets as well. 754 and 939 have not fared as well.
How long will AM2 and Socket F last? AMD may eventually release faster 939 CPUs in the future, but likely, due to the incorporation of DDR-2 memory controllers in their AM2 CPUs, it won't happen.