There are ultimately three choices you have as a UnityScript dev. Move to another engine, use Unity with C#, or give up. Since I don’t want anyone to give up that leaves us with two.
C# is Unity’s other applicable programming language. Unlike UnityScript, the C# used in Unity is more true to the actual C# language. This is a big strength because it allows for developers to not only learn a solid language like C# but be able to use it across other platforms and applications. If you transition from UnityScript to C#, it will take time but I believe it’s easier than switching engines. Unity has a lot of functionality in the engine itself, from its components to its animation systems to the debugging. Even if you switch languages, these systems remain the same and you already understand them. The only thing you need to relearn is the programming language itself.
For all the UnityScript developers, I would recommend sticking with Unity and transitioning to C#. It will take less time and you have much less to learn as opposed to learning a new engine.
(Thanks for reading! I am a not an expert on game development yet, and am always open to feedback. If you have any criticisms or suggestions for my articles, please let me know!)