I got a question the other day that kind of threw me. In that, someone asked if we were going to do a Silverlight version of AIR.
That's something you'd probably need to ask the executive folks around Silverlight (I'm just a guy whom uses the product, I don't decide on it's end to end features).
That being said, I do recall in 2006 a colleague of mine from omniEffect.com (Michael Wise) built what I'd call "AIR" via Java Webstart. We showed this off at WebDU 2006 as part of a presentation he & I put together (we later showed this to some folks at Macromedia whom were keen to understand the learning's of it all).
In this solution, Michael essentially embedded Flash Player Runtime inside Java Webstart. He showed how he was able to adjust the chrome, icon tray and basically have a desktop driven experience with minimal amount of effort (well his minimal amount of effort is my pain points but you get the meaning).
In thinking of this I wonder if the same approach could be had with Silverlight. I mean the two runtimes use a similar approach in terms of how they are housed inside browser agents.
I double dare someone to do it ( I am time poor and lack experience around Java Webstart's in's / out's).
Above is a screenshot of Flash inside Java Webstart. The point is, where there is a will, there is a way and I wonder if Multidmedia (Zinc) have approached this subject with fingers in both barrels.
As now, interoperability discussions can occur should the above hold water.