Jafo,
fact is: if you sell software with announcements like "this new features are coming soon" there is a good percentage of users that buy your software awaiting exactly this features. Yes, that's the world of customers. Really good for the company behind the software, an effective buying inducement. Welcome to the world of capitalism.
Imagine:
* Features coming presumably within the next 3 years (not sure now)
Don't you think you would have lost many of the purchasers that trusted in the announcement "soon" because they place value on the customization features (among other things)? You would have lost them, for sure. Quite rightly users trust in announcements like the one you made. And "soon" does not leave much space for an extensive interpretation, at least not for the meaning "years".
The main aim of announcements like this is the hidden agenda to catch additional purchasers. Don’t think we are stupid just because our world is not the world of software development. It's not the point that I can not grasp that this procedure is part of the "rules of software development". The point is that you instrumentalize promises to catch buyers and not even feel responsible for that afterwards. Sure, sometimes we all are wrong. But all the more it's necessary to grasp the mantle or simply to concede that you could have made things better (and still can). This is not sorcery, it's a question of decency.