I'm sure MorphOS is the best OS option for Pegasos, but I'm also a long-time BeOS user and I'm sure it's a great OS for PPC...
However, I'm sure it will be simpler to have Haiku on Pegasos than an actual version of BeOS, because it's obviuos that they will be trying to reach as many platforms as they can.
Hope Genesi will continue (or start?) the dialogue with the Haiku team as soon as possible...

@BeOS users in here: give your opinion! (And if you tried BeOS on PegXMac, let us know the results!)