What was the audience for IronRuby anyway? Ruby programmers out of all groups of programmers are the least likely to be using Windows now and most unlikely to consider it in the future. Plus, for deployment you're asking them to switch to Windows Server just to do what they can already do for free on Linux.
And would any interest come from the .NET side of things? I don't think so. C# prorgammers are more than happy with C# - lambdas, generics and the var keyword give you what you need. I think a lot of Ruby people when proclaiming the benefits of Ruby assume that C# is like Java was in 1995 when it's far more progressive. Add to the fact that Ruby is a pretty oddball looking language, I don't see many C# programmers being attracted to it.