We (a subgroup of OCaml developers including Leo and myself) met in November to discuss many things, including modular implicits. Leo’s plan is fairly ambitious, basically it involves making the module system of OCaml as powerful as general dependent types (has been done for module systems before, is not such a jump from the current system, but still requires quite some work to implement unification correctly), and there are still some orthogonal implementation questions that are still open for discussion. So more work is required, and since November everyone has been fairly busy with plenty of other things, so not much progress has been done I think.
(If you know someone interested in both the metatheory of module systems and implementation questions, willing to do an internship or some other form of short-term contract paid on research salaries, I would wildly guess that there is space for a year of work on these questions.)