We're at least a few years away before WebAssembly is really available for us to reliably use. Browsers just have to catch up. We'll be shipping unprefixed CSS grid before we're shipping WebAssembly.
That being said, I'm excited to see what we can do with WebAssembly. I expect it to add new people to the frontend community through projects like Blazor and the Go compiler targeting WebAssembly and I think learning from other communities is always a good thing.
I expect we as JS devs will still write code much the same way with perhaps a handful of heavy-load modules being doing seamlessly in the background via WebAssembly (like making PDFs or TensorFlow.js). On the whole I think the coming revolution with WebAssembly will be porting things like Unity, Unreal, AutoCAD, and other traditionally desktop applications into the web. This will democratize the web even further, letting people in developing countries have access to the same sorts of cool stuff we just take advantage of.