This immediately scared me away from developing for BeOS, even though I like the architecture and the folks at Be. Not really, because you still must compile to an x86 target. The introduction of another OS version of an application is unacceptable to most publishers, many which are already supporting both Mac and Windows platforms. All the incidental costs involved in producing all the variants and providing all the tech support won't pay off unless there is an overriding value for the end user who will buy the product. It is a serious chicken and egg problem.
Users wait for apps and publishers wait for users.
In the long run tech support would end up playing 20 questions to obtain a system profile before dealing with support questions. And although we may wish to think that current Wintel people would find using the MacOS easy and superior, some people who have used both actually prefer the Windows interface. I think expanding Apple's market share using the Diamond strategy, although possible, would be difficult and this is not a battle Apple should fight. However, in the long term I do think MacOS on x86 is going to happen but not through the Carbon APIs. They seem to be an interim solution.