I have heard from various sources close to Lagoon Park in Utah mention that the park is already in the development stages for their next big attraction. The three leading contenders are a water based dark ride, an interactive dark ride similar to Wonder Mountain's Guardian, or an intense roller coaster.
Our sources lean heavily towards the first two, and the ride is likely to receive a primeval theme to dinosaurs. The attraction is in very early development, as the park is still upgrading and banking off the success of Cannibal. 2020 to 2021 may be around the time frame that this ride could be complete.
ART Engineering from Germany is likely to be involved in the design and manufacturing of this attraction, given the park's past of working with them to create "in-house" rides. Some of the company's most famous projects include Cannibal, Wicked, Bombora, and engineering on the Triotech dark rides. While they are not exactly a household name in the industry, they have been growing as of recent.
If the park truly is leaning towards the dark water ride concept, they will likely be interested in ART's raft ride model. It is described as a cross between a traditional raft ride and a log flume. The budget for the project is slated to be around the cost of Cannibal, which after modifications totaled to around 26 million dollars. Lagoon would like an extended version of the model to go through a show building or man made mountain.
This is all initial speculation, as the park could very well decide on another roller coaster. With a collection of 10 roller coasters in their lineup, and Cannibal becoming their first hyper coaster, they may be holding off on another coaster addition until they deem it necessary. The park currently holds 2 dark rides, and 2 water rides.
As for 2018, it seems as though the park is looking to make infrastructure upgrades, and rehab for Roller Coaster (the park's only wooden roller coaster). Roller Coaster is slated to receive track work and new trains. It is unknown who will be providing the trains, but PTC will probably not be involved. GCI's Millennium Flyer model, or an all new design from ART may be explored.
UPDATE: Lagoon has filed a trademark for the name "Primordial", and links it to use for a roller coaster. Take that for what you will. This could end up being a ride system very similar to Wonder Mountain's Guardian. I have also heard that 2019 was being thrown around for the year.