I wonder if either the MorphOS Team or Hyperion are going to backport their OS's to the Natami?
Whichever gets there first (AROS, MorphOS, Hyperion OS4) could become the new defacto standard for 68k Amiga OS. 
Since both OS4 and MorphOS are PPC only they will never be "back ported" to the Natami board. AROS 68k is very probably though, but I think AmigaOS3.1 to 3.9 will be used by most people on the Natami when it is first released.