AMD says 16-core by 2012.
I think they were emphasizing 16 THREADS rather than 16 cores. Since 2007 for AMD will mean 8 cores, moving FX to quad socket in 2008 would actually produce 16 available threads though I think the next arch should be a "modular-threaded core" with 2 threads per core or the ability to use an APU to run extra threads.
Intel has shown that they can get an MCM out quick and with Penryn/Nehalem they can get 8 cores in one socket. AMDs tact would have to be different considering their more limited resources.
As I have always said the CPU competes with the SW and if SW is not ready for 4 cores, then having them has a limited effect on productivity and vice versa.
APUs will be a staple as you could offload even more background processes, such as 24bit 192K audio or TCP/IP, Java, .Net or kernel functions even(this would require extensive security modeling).
All of this of course is based on the proliferation of SW models but a little R&D can go a long way to provide proof-of-concept reference devices. A lot of the time required for new concepts requires less investment than research. It's hard to get a company to jump on new concepts that are unproven.