Votes expire over time
One issue with collecting user suggestions and pledging to act on them is that the value of the suggestions may decrease over time — some new feature that seemed relevant 6 months ago might be entirely irrelevant now. This is exacerbated by vote counts. If you are attempting to implement the most popular suggestions, but many of their votes were accumulated a long time ago, those votes are now less relevant and are skewing your work towards less relevant ends too.
My vague idea is to have votes wear off or expire after a certain period, perhaps configurable per map to account for development speed. The faster you implement suggestions, the less this matters, and the slower you move, the more chance you have of accumulating irrelevant votes. For our product Exist, for example, we have popular suggestions from years ago, and it makes sense to me that many of their votes would now expire. Their users may not use Exist any more, or may not find that suggestion relevant to how they use Exist now.
A second part of this feature might be to email users when their votes expire, giving them a chance to reapply that vote if it’s still relevant. I don’t see any harm in that, as only engaged users will bother to add their vote back again — and those are the users that matter.