In the conversation above, the customer pointed out that the question is critical for him, and this is a big call-out: it means he is not just wondering about this new feature, but he is interested in it. It is a well-known cliché about someone working on something that someday will be available to customers (like many other clichés, actually). Thus, you have to eliminate right away any objections, doubts, and mistrust.
If you are the first to admit that your answer is not the best one, the customer will not repeat this conclusion. It is probably very likely that he will penetrate you, and as he notices honesty in your answer, he will not be upset that much.
By the way, this approach is universal, and its formula is just like this: before sending a response, think about the apparent adverse reaction to it, and then add it to your reply. Just like when we were children: first who tells the story – \tells the truth; and it does not matter who broke that teacup from the tea set.