AFAIK the only way Apple can enable Nitro for 3rd party apps without enabling executable memory pages generally is by separating JavaScriptCore (and WebKit render engine) into separate processes (ala WebKit2 / Chrome) which are allowed to create executable memory pages.
Then, of course, there is no way to create bindings between your code and the JavaScript interpreter (at least not without the overhead of IPC, which would probably negate any benefits of enabling Nitro).
Then, of course, there is no way to create bindings between your code and the JavaScript interpreter (at least not without the overhead of IPC, which would probably negate any benefits of enabling Nitro).
So yeah, I wouldn't hold my breath.