> I wonder how OCaml and Haskell managed to keep implementers active.
Members of that community could probably comment better than I, but it doesn't hurt that Microsoft Research supported two core Haskell team members and Inria has supported core OCaml work for most of the lifetimes of the projects. Their better corporate focus has also meant that as some fabulously enlightented BigCos took dependencies on them (most notably Standard Chartered for Haskell & Jane Street for OCaml), they've both hired core developers and supported the communities. I should add that these have been fantastic for the PL community in general and specifically ICFP funding & attendance!
For as much as the members of any one community might have differences of opinion with the choices of the others, success of any benefit us all. Even if we do grumble occasionally with the "can't get into ICFP this year unless you're in language {X}!" comments, where X was Scheme, then ML, then Haskell... :-)
> people are not really prototyping the new ideas
Yeah, John's group plus Matthew Fluet and a little bit of myself are trying to clean up Manticore enough to do a "final" release and journal paper, and that is kinda taking up a lot of our extra cycles. Several other folks have either retired or moved on to new areas (security, compiler verification, etc.).
I think that if we could find some places where the new ideas intersected with interesting novel (read: fundable) research topics, there'd be some additional energy into implementation work around them. Right now, certainly, stuff exists, at best, in private forks of (typically) MLton.