Certain boards are generally bulk ordered for a specific model. That's the real problem. Once a new socket type comes out if not simply another model board supporting faster memory as well as a faster cpu the next generation of laptops seen is all too common.
Shopping for a Socket 423 or 478 board at this time and then paying out to have it installed would be up there pricewise a little too much just to see a faster cpu. That's the unfortunate reality. Some new model portables are now seen as low as $400- with just a blink of an eye from previously seeing them typically priced from $899-$1,400.