Add URI Language Identifier to core?

I voted No, because I do not want the framework to dictate how I choose to handle multi-language implementations.

This is absurd sentence .. How you handle languages in a PHP script ? with CSS / JS or with PHP ?
And if you use CI for your PHP code why not to have an easy option to manipulate languages?

And at the end, you are always are free not to use it but to think for another faster and better way to handle languages..

Like query strings? Language subdomains (i.e. en.example.com; this is more common for large companies)? Stored in a cookie or session variable (possibly even on top of a user profile setting)? The HTTP Accept-Language header (in fact, this is the only method that you can argue to be a standard)?

There are many ways and preferences on how to implement this, and there's nothing absurd about the statement that you quoted.

Its absurd because developer always will have the option to decide either to rely on the framework or on something else..

50% of devs may not use such element but other 50% of devs may use it. 
I think that 50% are more than enough add it inside the framework. 
And no one from the 1st 50% will be forced to use it. 

Sure, you won't be forced to use it, but having it built into the very core of the framework is a form of endorsement, an officially supported method, or whatever you wish to call it. And that is for a feature that can be implemented in at least 5 different ways that are already mentioned in this thread, meaning that we'd be satisfying 1 of 5 perfectly proper and valid use cases, leaving the rest of them uncovered.

Having that said, how would you like it if we chose another one of the 5, one that you wouldn't want to use? Wouldn't you feel that the framework is (indirectly, but still) dictating how you implement language switching?

Also, you say 50% is more than enough, but 50% of what? And how did you come up with that number?
Is it 50% of CI users? Or is it 50% of CI users that do implement language switching?
That is pure speculation, considering that (as I already said) it's only 1 out of 5 possibilities.