As the WebAssenmbly group is starting to define a design for future binary in-breowser executables, I think is a place where nim can shine. The MVP is aimed at c/c++ so generating code for this new platform may be not so hard.
https://github.com/WebAssembly/design/blob/master/HighLevelGoals.md
http://arstechnica.com/information-technology/2015/06/the-web-is-getting-its-bytecode-webassembly/
Right now Nim doesn't work too well (i.e. crashes) with Emscripten because the garbage collector scans the stack conservatively. At least that's my theory. It would be nice if somebody could have a deeper look into this.
Back to topic: It's interesting but also not really surprising: For quite some time now the browser is trying to catch up with traditional operating systems. ;-)
WebAssembly is a joint venture including people from the PNaCL group (and emscripten).
"Who: A W3C Community Group, the WebAssembly CG, open to all. As you can see from the github logs, WebAssembly has so far been a joint effort among Google, Microsoft, Mozilla, and a few other folks. I’m sorry the work was done via a private github account at first, but that was a temporary measure to help the several big companies reach consensus and buy into the long-term cooperative game that must be played to pull this off."