Hi
The ECS/Job system is definitely interesting, most interesting being the Burst compiler which I really like.
I do not have any concrete plans for it yet, when i do implement it I would likely start with either RVO or the recast graph, both of which I think could benefit from the burst compiler (not so much the job system though, as they are already multithreaded). The downside of converting movement scripts like AIPath to ECS is that it increases complexity and reduces readability, especially for users that are new to Unity. Those scripts are the ones that users are most likely to look at and edit, so I am kinda hesitant to increase their complexity too much.
20k entities is a ridiculous amount though…