The new Discovery sounds great.
Steve Gorman also confirms the addition, stating that the ride is already ordered for 2019 around the 7:00 mark of this Facebook Live video:
https://www.facebook.com/GoErie/videos/10156140589332367/UzpfSTE0NzUyMDgwNTI5NTk1MjoxNjAwNDYxMzczMzM1MjE0/
ACE mentioned a Mini Discovery, but based on Gorman's words, definitely sounds more like a Discovery Revolution (which Screamscape has mentioned).
Great add to the park, IMO. I would like to see the train station moved back a little bit, but not sure if there is a "re-profile" going to happen with that or not. The train station made a lot more sense back in the day prior to the moving of the Scrambler, but now it seems as if the main station is crowding the area a little bit.