One thing, though. What coasters can Alton add? What is silent, goes under the treeline, and not to mention, doesn't seem like a copy of another ride in the park?
They could get another accelerator (no need for a lift hill). Bye Rita.
Another Invert (thrilling even if it just sweeps the ground)? Not with Nemesis around.
A family ride? Likely, yes, even though there are several around alredy.
A woodie? Too loud.
A sit-down non-launched looper? How? (Blitzcoaster!!!)
They have sort of used all options already. They can't have any towering coasters without making the neighbours go bananas. An eventual launched coaster would have to be different enough from Rita to not detract attention from it. A gimmick coaster like a spinner is already used, and a dark coaster a la Eurosat would take attention from the 2010 ride. Anything drop-focused would instantly get into a competition with Oblivion, same goes for every coaster that goes underground for major sections of the ride.
By the way, let's not forget the Launched woodie... Oh wait, no. Let's do.
The major rides could be flats, shows, dark rides, exhibits, anything, but on the coaster side, there are very few options. It would be very optimistic to hope for three coasters in the next ten years.