What about the mods and plugins?

What will happen to the mods / plugins that are created for unturned. Well, as I understand it, Unturned 2 is going to be made in Unreal Engine. Will that make mods useless and have to be re-done?

Pretty much, I believe. All mods and plugins that were made for Unturned 3.0 will have to be remade for UII due to the engine change.