Being loyal is a two way street to me. If you are going to support a product over an extended period of time then I believe there should be some sort of incentive to continue buying the new version - especially when the new version only has X new features added to it. Those new features are really the only thing existing users are paying for, while new users are paying for every feature.

It doesn't have to be approached in the typical upgrade fashion either, the companies can treat the program as a completely new one but I would like to see some form of promo codes that only existing users can take advantage of in order to show appreciation for their support of your product.