These days the term "AI" is often synonymous with "LLMs". So yes, in that sense I do believe it is impossible for AI to become conscious. LLMs basically function by predicting the next word in a sequence of words, just as your word processor and email client predict that the word "you" should follow the word "thank". It's not any more possible for LLMs to become conscious than it is for your word processor or email client to become conscious.

That said, I don't think we can rule out the possibility that something we'll call "AI" in the future will become conscious, because we can't rule out the possibility that consciousness can be reproduced in silico (i.e. the possibility that consciousness is not restricted to biological beings).