What web APIs are you waiting to see adoption of TOP? For me its:
https://wicg.github.io/local-font-access/https://w3c.github.io/webcodecs/ More academically, I'm not so interested in an "API" per se but the ability to execute a JavaScript program as a webpage itself, as if directly accessing a JS file was as if you loaded an HTML file with the equivalent of <script src="file.js" />, such that the rest of the webpage could be brought up through the DOM manpiulation APIs. It seems that what little HTML snippets that are still necessary are really like programs being written in 16-bit x86 today- which only exist because an x86 processor boots into 16-bit mode, or otherwise requires 16-bit mode to execute various legacy functionality- so you have a bootloader with the minimal 16-bit x86 program to enter the "real" 64-bit mode that the processor actually runs in.
Of course Webassembly could also do this, but it has no way of drawing to the screen. Natrually we can give it access to WASI, but it would need at least a DOM API (if the DOM plans to remain relevant into the future, and its questionable if this is even desireable), but more interestingly just the canvas APIs are sufficent I think. Not that the HTML required to ratchet into JS mode is signifigant, but the JS required to bring us up into a reasonable WASM execution environment can be rather large, even if current "toolchains" bloat it unncessarily.