Epic has no interest in taking any of into the main branch so it’s always going to be a separate one Nvidia maintains.
It already has, literally everything you’ve seen on it has been in the UE4.
/tree/CataclysmDemo
Nothing, it’s still .
/tree/FleX
Depends on whether or not they have the time really, it’s inconsistent. Sometimes it’ll skip a version or two. You can always do it yourself though in theory.