to be fair i'm expecting the the mysterious race to turn up as part of some kind of expation at some point.
They've already said tons of times they're planning a campaign for the expansion

It would only be logical to assume the 4th race will be involved

Most of people won't know this, but not too long before game launch, Blair basically told the beta testers that a lot of things were "in motion" as it were.. they already have ideas and plans, and most importantly:
THEY want to finish telling the story, which is pretty much all the encouragement the player base should need - because it means we don't need to ask for it, we'll just get it.

But not an expansion pack, make it a patch
This can't happen, too many game changes to make it a patch. A good campaign would be a major project, a lot bigger than a patch.