Is anybody working on import plugin for nif files?
Unlikely.
Nif is the proprietary format for Gamebryo. Why would anyone write an importer for UE4?
There is plenty of free content done by community for Skyrim/Oblivion. I don’t think that selling this free content would be right, but using it as proxies to speed up development/play with ideas should be ok IMHO.
why would you want to import .nif anyway ?you can export your nif file to any format you want.
use nifscope