Instead of buying an Extreme4 and a 3570K separately, you'd probably just be buying an Extreme4 3570K. Kind of like how graphics cards are sold board and chip combined.
Point is, you dont know that. I have a feeling only high end mobo's will be sold with high end cpu's. For instance, you dont need that much of cpu power, but you do need a lot of SATA ports or other stuff on a feature rich mobo board. You will prob be stuck with an high end mobo which than comes with a high end cpu.
But we should all just wait and see how it all turns out And if intel does do it, i will probably go with AMD seeing as that is probably my time to upgrade again :P
enthusiant pc's will never die aslong as stock settings are in place. (since a factory setting will never use the full potential of a CPU)
the same could be said for mobo to an extend (apple like approach that would be)
and even if they would be sold a single solid item (mobo+cpu) im sure there are still people who will manually swap the mobo/chip because the standard selections of chips/boards simply does not live up to what they need/want in a performance/usage PoV. (risky to remove BGA ones likely but if the reward is worth it nothing out of the ordinary)