I am watching the game gui space for a few years now, and to be honest, i am not sure what the right course of action is.
Freeablo recently removed libRocket (https://freeablo.org/?p=105
) not sure if mygui is the best choice thou.
Overgrowth switched their editor gui (in Beta 2), from embedded browser (awesomium i think) to imgui.
CEGUI seems to be the largest/active library in this space.
I don't have any solutions to offer but i am eagerly watching this space to see how it plays out.