This can work - a variation on what you think
Let's not call it OS X on x86, let's call it Apple Windows or something that won't get them sued like Apple iWindows.
Let's not assume any Apple software compatibility (sure things could be recompiled for it, but let's assume that Apple doesn't bother except for the basics). Instead, let's assume a completely different strategy:
Making use of QEMU to virtualize the x86 + Wine or Wine X to allow Winodws programs to run at native speeds. Apple could potentially buy or partner with (
Transgaming Technologies in order to acquire a version of Wine (Wine X) that has Direct X compatibility and works with tons of games.
So, what we would have is a rebranded OS X operating system (iWindows = stable, fast, pretty, secure) + Windows applications at native speeds. One additional benefit to this strategy is that QEMU, while virtualizing on x86, does code translation for PPC. All the IP that goes into windows compatibility for Apple iWindows would apply to running the same apps on PPC/OS X.
Could a strategy such as this work? It is interesting, isn't it? Apple would not be competing with itself, it would be competing with Windows and trying to get converts to Apple hardware.
With the CELL processor coming soon, QEMU may be ramped up to provide better x86 performance (on the CELL) than the fastest x86 as well. But Apple would need to invest quite a bit into this.
I am dreaming... but it is a winnable strategy, IMHO.