SuccessorML is an ongoing work in progress. It looks to add (among other things) misc syntactic niceties (beginning | in matches, string interpolation, do notation, etc), builtin unicode support, and modular type classes for ad-hoc polymorphism (hopefully somewhat discouraging Haskell's typeclass soup).

We haven't hit the limits of what the language is capable of and a major investment would drastically speed up the process.