Both MorphOS and AmigaOS4 has an internal betaversion since quite a long time that runs on the Classic hardware. The hard question is when will these be available to the public - and I have no answer, as probably no one has. :-)
We can but hope for them.
MorphOS is rumoured to do almost everything my version does on my Pegasos, so it should be a killer for Classic hardware. And probably the same applies to AmigaOS4 :-)