In terms of the next big coaster what I would love to see is a B&M hyper coaster or a Intamin Woodie.
With the hyper though a B&M would have to go over 150ft at least, and digging a hole for such a ride would be way too expensive. Maybe they would go for an intamin hyper as it doesnt use so much room?
A woodie would be easier to create a good ride experience with less hight but wasn't there an issue with the ground being too unstable for a woodie? Unless they have sorted that with the hybrid models or steel supports/wooden track.
Aside from those two I'd love to see one of the gerstauler or mack launched rides...think Maverick at CP, that could work well at Thorpe. But overal what they lack for me is an airtime machine.