If it runs on x86 hardware, it would mean the user would want to try another x86 OS, if user try other OS he will leave AmigaOS.
Yeah... MorphOS runs on MacMini, MacOSX runs on MacMini as well.
And guess what ? People are buying MacMinis only for running MorphOS... Guess having another OS isn't a problem.
What people don't seem to understand is that most people already got another OS (either on the same machine, either on a PC/Mac). So if they wanted to leave the Amiga, they could have done so.
There's no piracy argument: people who want to use the Amiga, will use it no matter what happens (and even if they have to buy an expensive Sam that runs like a 7 years old PC). If OS4 was available on PC/Mac, they would still buy it, since it would be a lot less expensive. And some more people could also do it.