well, 10 years ago you might have called a flash developer a web developer? or atleast they were usually both.
so with that in mind, adobe air is one technology that certainly brought some one time web developers to become mobile app developers.
survey:
“using single technology to develop for multiple mobile platforms (Android, iOS)
-will never become mainstream
-definitely a future
”
its definitely proven to have a very profitable present and future for app developers and I believe you can call it mainstream now. Unity and adobe air as examples.
Air devs have had some huge hits making big money. I like Air I dont know much about unity but im sure there are countless apps that earn huge
React Native and Swift for non-games. Unity for games!
That is only a partial tongue-in-cheek answer. If I have time, I’ll elaborate further. The short is that web developers will migrate to whatever mobile technology they can easily relate to with their HTML/CSS/JS background.