Ok, so I don't agree that it implies language cannot expand. I believe it's a bit more nuanced than that, I believe what he's trying to say is that it cannot expand sufficiently to truly capture the experience. We will inevitably dumb it down or lose fidelity or whatever. The 'unsayables' as he called them, I believe he felt he was trying to protect their integrity by saying we should not attempt to distill them down to words.

As for the I cannot experience what I cannot describe... I agree with this statement deeply. Well, I think it's a function of ego or whatever you want to call it. We go through life and are shaped by our experiences. As we continue to experience life, we have more and more beliefs bouncing around in our head as a function of more experience. Ahhh, this just happened, it's like when I did X, etc etc. As we get older we get more and more bogged down by these limiting beliefs until everything we experience is going through our personal interpretive filter rather than just being experienced for what it is.

It's the Buddhist idea of the finger pointing at the moon. Don't mistake the finger(thoughts, words, etc) for the moon (the direct experience).

Well, that's been my personal experience, until I started looking inside and poking around at my belief structure, I had noooo idea how much my interpretation of the world had been shaped by prior lived experience, personally, and societally.

In your cold example... If you had no word for it, I believe most people would end up using the closest approximation out of the words they do know effectively blinding themselves to the reality of this new/unique experience for them. How though, would someone know, ahh there is no word for this, lets expand the language.

Gotta embrace not knowing/the beginners mind, and in my personal experience this is a process of subtraction rather than addition.