It is still a bit early, but I'm majorly bullish on WASM for multiple use cases:

1. Client side browser polyglot "applets" (Java applets were ahead of their time IMO)

2. Server side polyglot "servlets" (Node.js, embedded runtimes, etc.)

3. Language interop/FFI (Lang A -> WASM -> Lang B, like wasm2c)

Why is #3 so interesting? The hardest thing in language conversion is the library calls. WASI standardizes that, so all the proprietary libs will eventually compile down to WASI as a sort of POSIX/libc like layer. In addition, WASM standardizes calling convention. The resulting new source code may not look like much, but it will solve the FFI calling convention/marshalling/library issues nicely.

I’m not sure how it solves the FFI problem. Lowest common denominator calling conventions don’t make it any easier to bridge languages than it already is.

C calling conventions are already the standard for FFI in native code, and that means dropping down to what can be expressed in C if you want to cross that boundary.