Mark Gurman of Bloomberg has another one of his excellent chip scoops, this time about the future of the Mac: The company, which released its first Macs with M3 chips five months ago, is already nearing production of the next generation — the M4 processor — according to people with knowledge of the matter. The new chip will come in at least three main varieties, and Apple is looking to update every Mac model with it. Apple’s moving through Mac chip generations fast—the M3 was introduced six months ago, but Gurman suggests that it will only be about a year…