@EyeAm
OS4 does run on classics provided you have a PPC card for it.
OS5 is vapourware like Duke Nukem Forever. At least 3DRealms has finally folded now. You can wait for Amiga Inc. to fold but that still won't get you OS5 on x86. Or any "officially" branded AmigaOS on x86 anytime soon.
If you want an Amiga like OS on your x86 box you're only choice is AROS at the moment.