Intel´s current dual-core Performance market is dominated by the T9800 CPU, which will be replaced with quad-core mobile CPUs. Of course we are talking about Lynnfield, quad-core 45nm Nehalem generation CPUs, and this transition will happen in Q3 2009.
Intel betting a lot on this strategy to kill off dual-cores and replace them with much hotter quads, but ultimately this will create powerful desktop replacement machines that won´t lack horsepower, but at the same time they might be hot and heavy.
Intel still doesn't talk about Lynnfield quad-core frequencies but we do know that this new platform relies on dual channel DDR3 and that it doesn't work with DDR2 memory.
You also have to count with some pretty saucy prices, as Lynnfield will sell from $300 all the way to $1000.