Ah yes within the browser space the various companies are just putting web assembly in/alongside the existing javascript engines. WAVM was just an example of a whole new vm that isn't for a browser, but does run webassembly.
Yeah; I probably should've been more explicit in my original comment: there's definitely new VMs being written for WASM, but none are currently expecting to go into browsers, hence concerns about sandbox escapes from browsers aren't affected by them.