I think the very near future will be web assembly code that paints a canvas. Mature desktop methods with GUI design tools will be ported to web assembler and retrofit for the web. QT5, imgui, are just the beginning.
I think a good exercise would be to open the Full Stack React book again and port the first few running examples to a Qt Quick Controls application and then target webassembler. I am willing to wager that anyone who gives it a real shot will be impressed at the productivity gains -- which generally stem from QML's expressiveness and not having to deal with React's over-complicated design. Not to mention, you'll not waste time because some component you made behaves differently across browsers. You'll also notice a complete lack of the dogma that tends accompany modern JS frameworks and libraries.
It also feels good to know that your UI may be a bit more performant that DOM based UI's.