When is Cortana coming to RT?

Maybe I'm looking in the wrong places, but I haven't heard anything about MS bringing Cortana to either Windows RT or Windows itself. The latter move doesn't make sense for a product in beta, but Cortana on RT could be a selling point.

What do you all think, did I miss it? Do we even want Cortana on RT? Is it ready for full Windows 8.1 now?