Not possible, not a huge enough community, unreal engine would be something completely new for stephen & Fredy i think, financial sides, not needed, would remove the charm, etc.
4 reasons this is not happening:
1) Unreal Engine 4 is bad for these kind of projects, just because it's pretty doesn't mean its good.
2) The scale of this project is something for a AAA company, not two coders and one modeler.
3) There's not enough demand for this kind of game to make it work.
4) PERP is still good enough to get a nice roleplay experience.
Not even going to try unless Russian had a flash game in mind but I have no knowledge of this kind of coding at best HTML, CSS and maybe C# or whatever it is. If I was going to make an unreal engine 4 game I would not bother since I know it would be a dissapointment.
As for my post I mean no offence to Fredy or Stephen I just do not see them using that engine really.