Six Flags Qiddiya, a planned theme park in Saudi Arabia, is planning on building Falcon’s Flight, the world’s tallest, fastest, and longest roller coaster, when it opens in 2023. We don’t know the exact height, speed, or length yet, but it would have to be at least 457 ft tall, 150 mph, and 8,134 ft long in order to claim the records.
https://content.sixflags.com/qiddiya/about-the-park/