It's really hard to create vendor lock in on a feature nobody uses.
But even if they did go down that route, NaCl is licensed under BSD, so even Microsoft could add NaCL to IE if they wanted to. That's some pretty weak vendor lock-in.
Licensing is not the issue. Microsoft could not add NaCL to IE in the same sense that it could not add Firefox' DevTools to IE. It would require a major rewrite and cost tremendous heaps of money.
Even if that's true (and I share the sibling's skepticism), vendor A's incompetence and poor product quality is not meaningfully described as "lock-in" to vendor B - especially so when there's a readily available vendor C (Firefox) that doesn't share these ills.
I've gotta raise an eyebrow on that one. If it's a major rewrite to support a new plugin authoring language, your plugin architecture was a terrible mess to begin with.
Given that we're supposed to believe that New Internet Explorer was pretty much a from-the-ground-up rewrite, I can't imagine that their plugin architecture is a terrible mess.
NaCl isn't simply a plugin architecture. It is effectively the entire Chrome sandbox and large parts of Chrome architecture made available to binary plugins.
You aren't pulling it into your project without also pulling in half of Chrome.
According to this [0], NaCl is a Pepper plugin. [1] This would strongly imply that all you'd need to do to use NaCl is to implement PPAPI. Care to point out how I'm wrong about that?
the PPAPI is very closely tied to chrome's inner workings and is extremely complicated to implement as, compared to the old plugin api's, it doesn't allow native code any access to the local system. So it needs to provide plugins with all the possible hooks they will ever need.
For other browsers to support PPAPI, they'd have to implement all of this, which, btw, also is a moving target that moves forward in lockstep with chrome releases.
But even if they did go down that route, NaCl is licensed under BSD, so even Microsoft could add NaCL to IE if they wanted to. That's some pretty weak vendor lock-in.