What I would rather see is an Apple-branded version of Linux that would function as an "OS X Lite" for generic PCs. It would have a good part of the useful functionality of OS X without cannibalizing Apple sales. For uses, it would be a low-cost way of getting some useful OS X functionality and connectivity with Apple products for networking and lightweight synchronization.
Is Darwin still an option?
Tried to find it via darwin.org and it seems to have been yanked into the larger Apple sphere of influence.