I think a good way of combating that is to get a page up for feedback submission. Anytime you have users like that, ready to make a decision based on your answer or lack of one, you direct them to that page and gently ask them to leave their suggestions for the team.

At the end of the day you need to be honest with your users, but do so without revealign what you'll be doing. Instead say that feedback and feature suggestion is crucial, but we can only support the most popular ideas for now. Which is the truth. If adding a feature is requested by 60% of your base, you know you're going create value by giving it to them.

Goodluck