Right now (13 november 2021) it are only some rumors. But according to these rumors Alton Towers will probably get a new B&M coaster from a yet unknown type, in the near future.
An as yet unknown coaster model at a location across the valley (between Forbidden Valley & Dark Forest).
A surf coaster could very well be possible because AT is not allowed to build above the tree line.
But it’s the expected location that is the main problem, so I don’t expect it this way. The opening of this ride could also be in 2024, if all goes well.
No official information about this ride is released yet!!