The issue is not that the bugs are with correctness of multiple dispatch, but that multiple dispatch allows you to combine generic programming with abstract data types. Thus, one can have a generic implementation in base Julia, and someone can pass a new user data type - a combination that can easily not work. Some of the frustration also arises from types such as OffsetArrays that are included in the base distribution, but not as well supported and tested as the regular Arrays type. Thus, the discussion here tends to focus on defining interfaces, and of course on better testing of uncommonly used data types.

In general, we've not had a formal roadmap - but we present a "State of Julia" talk at JuliaCon every year. But very broadly, the list (of the top of my head) includes: improving a lot of the underlying compiler infrastructure overall, improving support differentiable programming, improving garbage collection, support for GPUs from multiple vendors (too many of those now), supporting apple silicon, type system support for tools like JET.jl.

NEWS.md is generally updated during the course of a release cycle, which eventually becomes release notes, and then post release, we put together a highlights blog post. https://github.com/JuliaLang/julia/blob/master/NEWS.md