Great question.
We understand that our versioning scheme may have caused some confusion. Really the "pre-release" versions should have been released as 4.01, 4.0.2, 4.0.3, etc. Maybe this would have made more sense as the "pre-release" version are fully tested. The only difference being that they are released as patches versus a full install. We acknowledge this and will make this change effective immediately.
We have also done a ton of development for version 5 already and have completed proof of concept and testing for several new features to be released in Advanced and Professional Editions.
In the end, we want you to feel good about your purchase. The first year of maintenance subscription is provided at no cost and renewing your subscription with us is completely optional. If you feel that the current version meets your needs there is really no reason to renew.