> Pegasos I at least. Pegasos II eventually got an OS4 port

Pegasos I and II were designed for running Linux as much as MorphOS, so none of them were ever MorphOS-exclusive. And even if there'll ever be a PPC hardware designed exclusively with running MorphOS in mind, there's no way a later port of OS4 or Linux (or any other OS) to such hardware could be prevented.