I think sentience like most things is a spectrum, so I'm not really sure what you mean by sentient, but I would argue that for most people the bar for sentience is much higher than text prediction. The Chinese room is only one aspect of our minds, and we don't even know what consciousness is.
And to be fair, reasonable people stake out positions on both sides of this debate: I'm not claiming that the alternative proposition is somehow unreasonable. It's a legitimate subject of scholarly disagreement.
Nevertheless, I'm still firm on language. Why? Because all complexity is ultimately about symbolic manipulation of terms representing the process of manipulation itself. ("Godel, Escher, Bach" is a fantastic exploration of this concept.) How can you manipulate concepts without assigning terms to their parts? That's what language is.
The question I like to ask is this: are there any ideas that you cannot express using language? No? Then how is thought distinct from language?
Yes, people (myself included) experience a "tip of the tongue" experience where you feel like you have an idea you can't just yet express. But maybe this experience is what reason feels like. Why should idea formation take only one "clock cycle" in the brain? Why should we be unaware of the process?
I think this feeling of having an idea yet being unable to formulate it is just the neural equivalent of a CPU pipeline stall. It's not evidence that we can have ideas without language: it's evidence that ideas sometime take a little while to gel.
I think as highly social beings we often annotate all of our thoughts with the language we could use to communicate them, which could lead us to believe that the thoughts are indistinguishable from the language, but that conclusion seems like an error to me. I’ve also heard some people talk about how they are “visual” or “geometric” thinkers and sometimes think in terms of images and structures without words.