With the quick succession of CPUs with more and more cores, it's was no secret a few years ago that Intel planned to more or less abandon single-core design. It's no secret now that they also intended to even see the dual-core platforms wane in the face of CPUs with four, six, eight or even more cores.
The growth and success of dual-core CPUs has been so great, though, that they are staying on Intel's roadmap for a longer amount of time than expected. On top of the proliferation of dual-core CPUs, Intel is apparently concerned about the lack of multithreaded software that will make use of many cores in a single system. You can easily see the problem here: Intel sells a chip with 16 cores at 2GHz, and people get upset when an “ancient” system with only 2 cores at 3GHz has a performance advantage.
Because of this, Intel and many others expect dual core to remain king for at least through 2009.