You might be waiting till 2011 then for after socket AM3...AMD will ride this socket for a while it seems compared to their last few.
AMD came out with Socket AM2 in 2006 and didn't replace it until earlier this year with AM3. AMD tends to only change sockets with their IMC-equipped chips when they change the type of memory, so I wouldn't expect to see a successor to AM3 until DDR4 RAM comes out or
they make a major change to the CPU's I/O pathways that necessitates a new socket. DDR4 is probably
going to come out in 2012, so I'd expect AM3 to be around a while if AMD doesn't make any huge changes to their CPUs' I/O. I don't know if they would do that, but if they did, it would probably come in 2011 with the introduction of the K11 "Bulldozer" CPUs. I do know that the upcoming DDR3-using Opteron sockets C32 and G34 will support both K10-based chips and K11/Bulldozer-based chips, but those brand-new sockets may very well have a pinout that will support those upcoming features. AM3 probably does not support much that's not in current CPUs since AM3 CPUs work in AM2 boards, so the pinout must be pretty much identical between AM2 and AM3. That doesn't leave much in the way of future expansion, unless a lot of those 938 to 940 pins are "no connect." I can't find an AM2/AM3 pinout, so I can't tell you.