Developing mobile apps for multiple platforms

Much has been said about it.
Many think it would be great if there were a magic solution: develop once use everywhere.

In fact this solution has been available for ages. It's HTML + JavaScript.

But if you need to go deeper, you have no choice but native development. A very lucky situation for us, developers. This situation creates a huge number of jobs and business opportunities. I would rather ask whether anyone seriously believes that these opportunities should vanish?

For about half a century we have been having different computers with different OSs and all the attempts to make them all support "once develop use everywhere" concept just ended by creation of more development languages and platforms, though nothing has become as universally supported as HTML and JavaScript. So what makes you think the mobile sector will evolve differently?