Most if not all of them will land in the next few years. In fact, working on those precise features is what most of the OpenJDK team does.
> Improved native code interop. I consider this to be both a language and VM change.
That would be Project Panama, making its initial, partial delivery in JDK 14 (GA next March, EA available now).
> Improved memory layout control, including stack-allocated types and inlined objects inside of other objects.
Project Valhalla. The most complicated of the bunch. Just had a recent major breakthrough, and you can work with the EA release already.
> project loom for golang-style I/O programming.
Working on it :)
> full tail recursion. Why was this feature rejected from the VM?
Not at all rejected. It's still a goal for Loom. We'll just do lightweight concurrency first. Cost/benefit prioritization etc.