The dominatant system will simply be the one which prvides the following:
1. A customisable Amiga environment.
2. Gives good Price to performance ratio.
3. Has the "Killer Apps".
I personally think all three projects can forefill requirement 1.
The price performance requirement is a subjective one, depending on what hardware you have now, and how much it was cost to use the OS.
As for requirement 3... I'll bet that any app worth it's salt will probably be ported to all three... (Though I imagine, the MOS team and Hyperion could probably secure a few exclusive deals).
So... to me the future look uncertain, but then again I've already made my choice... :-)