Unfortunately there are a number of downsides which will inhibit cross browser adoption and standardisation. I would view NaCL and PNaCL less for the open web,

Unfortunately there are a number of downsides which will inhibit cross browser adoption and standardisation. I would view NaCL and PNaCL less for the open web, and more an attempt to position Chrome as a replacement for Desktop OS / application platforms. PPAPI, and LLVM are not necessarily suitable for cross browser adoption or standardisation. LLVM is a single implementation and so like SQLite, its likely it would not be accepted. It is also not particularly architecture independent nor language agnostic. Low latency polyglot JIT is an open research area on LLVM. PPAPI is a single vendors view on a suitable API. It focuses on a single vendors needs. The track record isn't there.