Here's the official press release from ICE:
https://www.theice.com/showpr.jhtml?id=6574
And here's a blurb from the Chicago Tribune about it:
Merc loses futures to ICE | Chicago Tribune
Look for the CME to make a push on their S&P MidCap 400 product (which has the same tick and point value as the ER2 Russell). The ticker symbol is EMD.
Remember, not only the ER2 mini is currently traded at the Merc, but the pit-traded RL big contract as well. Could be interesting to see how this one will play out.