I would buy MorphOS for Mac Mini, if there was any compelling reason to do so.
To be frank, I'm not aware of it having any advantages, now, or even planned.
I would be glad to be corrected. If it runs amiga software a little better...ok, for a few remaining amigans that would be good.
but I think people are talking in terms of an expanding market...so for the rest of the world, why should they bother?