I used to think the sandboxing feature was going to be a really big deal but I don't any more. I think WASM is eating their lunch in sandboxing. I'm keeping a close eye on Fermyon and Dapr.
Deno runs WASM code just fine and IMHO will probably be the pre-eminent way to use server side WASM (because you likely also need some JS/TS bootstrapping or glue code too for setting up a basic API or other endpoints): https://deno.land/[email protected]/getting_started/webassembly
If you're writing your server side code in JavaScript, yeah. I don't think it will be pre-eminent. I think it could be popular but much less popular than Node.
There are server side WASM runtimes for other languages, though. Including ones that let you write endpoints entirely with WASM (and its languages like Rust and Go*), like Fermyon and Dapr.