When V8 came out was around the same time I stopped programming in C++. I still love QT but was very under impressed by the JavaScript engine in QML. I have moved most of my focus since on JavaScript and Node.js (and even Microsoft Jscript.net for a time) because of the speed at which I could develop complex business applications and network applications.
My love of V8 makes it emotionally hard to accept a new V4VM but the arguments made in here seem valid and I think this may convince me to move ahead and try out QML again. It's either that or Electron.
In terms of the future and general popularity of QT, there could be nothing better than JavaScript QT. going head-to-head with Electron. However, my personal preference would be doing this without XML. I wish I could just code QT in JavaScript similar to how it's done with C++. There is a QT npm for node.js but I couldn't get it to compile... clearly not well maintained.