I have to say I'm not convinced by the arguments in favour of tinkering with the language. For all its deficiencies the Revised Definition does give us a document where we can agree on what is or is not Standard ML. The proposals I have seen appear to be fairly minor changes that really make little difference to real coding, perhaps saving a line or two here or there. I really wonder if it is worth the disruption.
I think the problem is that any change seems to involve adding complexity to an already complex language. When I did my PhD I was heavily influenced by Tony Hoare's 1980 Turing Award lecture in which he argued that the successors to a language were usually worse than the original. In his case he was comparing Algol 60 with Algol 68 and Pascal with Ada.
I wonder if it is possible to design a modern, small strict functional language. I certainly think that a language where most of the data is immutable has enormous potential particularly for parallel or distributed applications.
David