If you're asking for a Planet Coaster mobile game then I think that needs to wait until after PC release to see if it's even worth it. The mobile gaming environment is much different from the PC gaming environment. There is a much wilder variety of hardware platforms to account for when going mobile. There's also the challenge of different business models. The entire project would likely need to be a whole new game. Maybe they could re-use some assets. I'm not sure the risk vs reward trade-off is worth it. Simulation games do not have a good track record on mobile. I'd even argue that mobile games hurt the IP they're attached to (see SimCity and RCT).
If you're asking for a Planet Coaster companion app then no -- it's a bad idea. Companion apps are nearly always garbage, poorly maintained, and forgotten after a short period of time. It's hard to even recall the last game I know of that had a companion app because they're all so forgettable. I suppose there was that companion app for Evolve that would give you an unfair advantage in game. I remember that one because of people complaining about it basically being a way to cheat the progression system. I surely did not buy that game!
tl;dr Mobile simulation games are high-risk. Companion apps are a waste of resources. In a perfect world maybe these would be nice, but in the real world it's not worth giving up the stuff that would be cut from the game.