There would be pretty much 0 market share or need for a dual CPU laptop. The power and heat dissipation requirements would be too much for a "laptop", the size would probably be too much as well. To get to a speed where dual CPUs wold make sense over a single high-end CPU you'd have to go over what a good i7 CPU can get you, so we're looking at a laptop with a price point and size over the current $3,000 laptops with the only advantage of it being a built-in screen. The cost to engineer a laptop case and motherboard to support 2 CPUs would be well over how many could be sold to break even.