An experimental chip from Intel shows building a kilo-core processor may be possible. During the Supercomputer 2010 conference held in New Orleans last week, Intel researcher Timothy Mattson said the technology in the Intel 48-core Single Chip Cloud Computer is "arbitrarily scalable" and could support 1,000 cores on a single processor.
1,000 cores seems to be the limit for now; after 1,000 cores the on-chip network connecting all the cores will grow so much it would negatively impact the performance of the chip. The chip is still only theoretical and in the experimental stages, and Intel doesnt have a processor of this size on their roadmap, so dont expect to get your hands on one anytime soon.
Intel has been adamant that the future of processors will depend more on the number of cores rather than the overall speed.
If only the software could keep up with the technology -- despite the technology for dual and quad core processors being around for years, games and other programs have only recently added support for multi-core processors.