I don't know about the E-M1, but I discovered this past weekend that the Panasonic GX7 did a good job of photographing an 8th grade basketball game. See the link to the set below.
http://www.flickr.com/photos/30161756@N00/sets/72157638451234325/
I used the Panasonic 25mm f/1.4 lens...not the farthest reach, but decent if you are close to the court. I shot in Shutter Priority Mode with SS at 1/500 sec. and ISO set to Auto. Most of these photos were shot in burst mode, as well...which is a testament to the lightning fast AF of the GX7. Also, out of the 300+ photos shot, not a single shot was out of focus...another testament to the very high performing AF system of the GX7. I think when paired with the proper lenses, the GX7 can make a recent sports photography camera.