I have a young project yet, just did the architecture of the classes and most of the base game functionalities. Soon to implement guns and skills. But I wonder if it’s worth upgrading or not?
The process is time consuming. That’s why.
Unreal Engine 4.11 has Optimization improvements so that being said if your planning on porting the game to a Console or just want better frame rate on PC then I do recommend you Upgrade to Unreal engine 4.11 , consoles can run stable and look gorgeous while PC will run a bit better depending on your PC and it can help people get to higher settings or just have a little FPS boost 
You said that your project is still young and that you only did the architecture , Unreal Engine 4.11 has a slightly better rendering system so it will look better , run better and it will have more features + the latest SDK’s
Good luck with the project !
-Edwin