I was watching a video on Youtube and they were making a point on how the 'app' gap war is now being superseded by the 'assistant' wars.
Eventually, if Microsoft, Google, Apple and Amazon have their way, you wouldn't need a banking app, or an Uber app, or a shopping app - instead you'll just ask Cortana, Siri, Google Now (or whatever they're calling it) or Alexa to check something, order a cab, buy some apples etc.
So, I would suspect at MWC, Microsoft will mainly be concentrating on Cortana (and possibly Skype chatbot stuff which is similar). If they can also crack voice-recognition Windows Hello, that'll give them a very big event for MWC.