Trademarks and copyrights are a bit of a jungle - they need to be renewed to remain active and sometimes a renewal doesn't really mean a thing. However, when Microsoft themselves tweets about it as in the case of Killer Instinct, well then you can probably bank on the fact that something is on the way.
With all due respect to our friends in the media who like to frequent trademark sites, we thought we'd break this one ourselves. :)
Our legal eagles have authorized us to say: "We have either renewed or refiled a trademark application in various jurisdictions."
Given that the news broke through Play XBLA it's reasonable we'll see some kind of remake of the originals or perhaps a Killer Instinct 3 on Xbox Live Arcade in the future.