Games Workshop just released a video teaser showing us the Astra Militarum fighting Tyranids. Of course it is a swarm of Tyranids they are showing, so possibly something else coming in week 2? Could even be a bundle release or two coming?
Here is a link to see the video this morning. Its nothing spectacular. Not even a flash of the new models in there (unless I missed something).
https://www.youtube.com/watch?v=0zW680GyuH0