Sometime ago, I decided to take a dive into Belenix again.
As of today, I've got a working rpm5 and smart package manager setup on my computer.
I've posted a roadmap here : http://mail.opensolaris.org/pipermail/belenix-discuss/2011-July/001510.html
I can report that I'm on track, and hope to have an IPS repository for rpm, as well as the beginnings of an rpm repository by the end of this month.
The recent news about Joyent's port of KVM to Illumos, as well as today's announcement of SmartOS are both very exciting. It looks like there's much to achieve ahead !