of course the viable platform argument was lost a long time ago...probably around 1996 the platform lost viability and sustainability.
However, we have bottomed out and I believe the community is at a new sustainable level.
if you count all users... the germans and the english speaking world...the 10 people who use aros ;-), AmigaOne owners, Pegasos I owners, uae, Classic Line, and people like me who just post for apparantly no reason..(because we don't own any Amiga, don't use an emulator, don't use aros, and have even lost any sense of being uncomfortable about it).. I think that number is closer to 3000. I don't know that that number is important as its too diverse a group to reach with a product.
I do think an Amiga OS 4 or the Pegasos II, can be a viable product, however. It's just that they will have to attract new users. There are lots of people interested in new OS's and new fun computer systems.