I see where you're coming from, but perhaps a better way is to make it possible to offer discounts for a new app. E.g. Funky App 2 at half price, and to be able to notify users of the app at that new price.
The rationale behind this is that users can still be notified of major release versions without forcing them to upgrade or die (sometimes people continue to support older versions for a bit while the new version gets traction). For example, the new version of Coda when it came out was pretty buggy compared to the older more stable version and app store reviews showed it, but there's no way for people buying Coda 2 on the app store to upgrade to Coda 3 at an upgrade price when it comes out. Having the ability to provide a discount for not only Coda 3, but other Panic software at upgrade time could generate more sales for things like Transmit etc.
I'm not singling out Panic, just a recent example.