http://www.90-9-1.com/

The 90-9-1 rule says that 90% of people are going to be consumers/audience, 9% will interact/edit/participate, while only 1% will be doing the actual creation of content for people to interact with or consume.

The desktop Macs are for that 1%. In fact, most computers have been designed to cater to that 1% of coders and creative professionals. Very few computers have been explicitly designed and made for the other 99%. The iPad seems to me to be targeting that 90% that want to be an audience/consumer of content, but are not creators. It's a computing device/appliance finally made specifically with them in mind, rather than with hackers/creators/coders/geeks in mind as the target market.

So, it makes sense that Macs will remain the only way to develop for iPhone OS. Making iPhone OS capable of becoming a development platform would be counter to the entire idea/market of iPhone OS.

Macs may dwindle to 1% of Apple's sales some day, but they'll still sit at the top, trickling down all the content to the rest of the ecosystem.

Imagine a world in which Apple never created the Mac, but had instead been formed many years later, with the same people, processes, and design ethic. They'd still have become successful at selling iPhones, iPods, and iPads; nothing about those devices really depends on the Mac legacy, except for the fact that their OS happened to have been developed for the Mac first. In that world, if you walked into Jobs's office today and pitched him on the idea of launching a line of traditional personal computers, he'd say something sarcastic and tell you to GTFO. The idea wouldn't merit five minutes' thought.

Hence the company's new name, sans "Computer."