A high level manager told me what the Mississippi poster means:
A new RMC Raptor for Worlds of Fun.
The clues are all in the poster:
1. Here is the original poster and coordinates: https://twitter.com/CPFoodBlog/status/1022125680803414016
2. The first clue in the poster refers to passage across the Mississippi. The origin is Cedar Fair headquarters at Sandusky OH. Crossing the Mississippi, you have 4 parks: Knotts, CGA, WOF, and VF
3. Knotts and CGA received coasters last year. That leaves World of Fun and Valleyfair.
4. The second clue is from the coordinates. They are: 37.8399 N 77.4442 W, 37.3984 N 121.9752 W, or Kings Dominion and CGA, respectively.
5. A weighted average of these 2 coordinates gives: 37.61915 N 99.7097 W. This location is surprisingly close to World of Fun, which is 39.1767 N 94.4867 W, and certainly much closer than to Valleyfair.
6. Finally, the mine train refers to a smaller coaster: an RMC raptor.