As much as we would all love to see Apple succeed in every area of technology, it's unrealistic to expect them to do everything. They happen to be making a lot of money AND getting promotion for their computers from the iPod/iTunes thing. It isn't that Apple is abandoning making computers AT ALL, it's just that the iPod is what's hot/hip, and by no means are they going to say no to that.
Besides, it isn't written in stone that Apple has to make money in the same market(s) as MS, Dell, or whomever else. If they can market peripherals and/or computers to different markets more effectively than others (like film and design companies as opposed to business) then more power to them. I'll still buy one as long as I still like them. They don't need to compete in markets where the returns would be too small to warrant the attack (like business, games) even IF they succeeded.