Pretty much a zero probability...
With Macs being Intel based now and with the ability to run other OSes through either virtualization or dual boot, I think there is zero chance Apple is going to devote the resources to porting to Windows.
If you don't have a Mac, get one for your next computer. When you really dig into the hardware, the Apple premium is pretty minor (or in many cases, non-existent), especially if you're a serious developer and you intend to make a living developing for the iPhone.