Softimage's program manager's current position is to not have iray in softimage. Not because it's awesome and must be reserved for Max, but because isn't so hot, and it isn't useful for most of the user base (everything must fit in the GPU RAM for using the GPU, no motion blur, no programmable shader trees, no particles, etc) and is costly to integrate and maintain. (It's not going to be in Maya either, afaik) The time that would be spent on that will be spent instead on the OpenGL Viewports, maintenance/stability of the current rendering engine, and helping third parties such as Arnold.
I actually find this to be very disappointing news. Yes there are some limitations, but aren't there limitations with Mental Ray currently too? Does every render need motion blur or particles? There are a lot of projects that are Viz centered and iRay would be great for that. So far the current implementation of Mental Ray - well, I am sure you have read all of the numerous posts about it over the years, and can come to the conclusion that it is not that hot and very slow in its current form. Yes, Arnold would be great - if some of us had access to it. It would have been nice if this was posted a long time ago to let people know the roadmap, but at least you did it now, so thank you for that. I just hope that when things do get added for the new Mental Ray (I posted a thread link to it a couple of pages earlier) that they get implemented quickly and not dropped halfway through without being seen through to the end...
I thought this was nice:http://www.youtube.com/watch?v=J0zZnjasxBY&feature=player_embedded