Here is the way I see it:
Userbases are hard to come by. The only real ones left besides the big 3 (windows, *nix and Mac) are BeOS, Amiga, RiscOS and Atari (with *substantial* amounts of users, albeit small). Atari is pretty much a null point, seeing as how new hardware is just not in the cards for them.
It took MorphOS and the chance of someone else making money from the Amiga user base to finally spur development of OS4. In the interim, this is a good thing for all of us, as competition always results in the consumer winning. In the long term however, it will, as predicted, drive a wedge between the userbase until either:
A) there is a clear winner, or
B) one of the companies either gives up or dies.
Now, perhaps others won't see it the same way as I do, but OS4 is obviously the natural progression for the userbase. This isn't MorphOS bashing, its just realistic. Developers will start coding for MorphOS' Q-box, which is essentially no longer Amiga (granted, ExecSG isn't the same as the old core, but it does retain the original design structure if I'm not mistaken, i.e. the scheduler and so forth).
I think Amiga does have a chance at survival if they can retain their current userbase and target the right commercial markets. I think as soon as we see a good web browser and java support, we'll see a slight resurgence, especially in Europe. After that, its up to developers to give us the tools that:
1) for the home users, allows us to be able to use it to fulfill most of our computing needs, and
2) give the commercial users a compelling product, an innovative product, at a price that that can sell it to businesses *and* support development.
Obvous, if you think about it.
8-)