The real "Write once, run anywhere" technology is the open web platform. Now with SIMD, WebGPU, Houdini, and more. Container queries built-in for responsive layouts. Run on touchscreens, virtual reality, desktop and more.

I expect HTML/CSS/JS performance optimization to be valued as a skill more. It is arguably great cross-platform technology (though lacking native widgets), but it has a lot of performance footguns, which we need people to be disciplined about.