Next thing would probably be an OS. With different APIs, the browser could be not constrained by existing standards. Generation of a good set of applications making working in the OS convenient - starting with GNU set? And then we can approach CPU architecture - again, without constraint to existing languages or instruction sets. That should be interesting to play with.

Someone has already done this: https://github.com/viralcode/vib-OS

Also, someone made a similar comment not too long ago. So people surely are curious if this is possible. Kinda surprised this project's submission didn't got popular.