[pjmlp]

There are already ongoing efforts to port JVM and .NET environments into WASM, although currently it is more of a proof of concept.

When WASM gets mature, expect the return of the plugins, maybe even a Flash to WASM compiler.

[hajile]

I don't believe the answer to JS is downloading, and compiling the entire JVM.

[pjmlp]

As I mentioned, It is already happening.

https://github.com/SteveSanderson/Blazor

https://github.com/kg/ilwasm

https://github.com/konsoletyper/teavm

In two to three years time, Flash will be back.

[sqeaky]

I think you are adding extra steps that are not needed. The programming model requires the JVM there are a few tools that compile Java directly to native code. There are tools that compile it to java script, and there are beta quality tools that compile it to WASM.