I wish it were that simple
. This illustrates the silliness of it all and the completely ridiculous assertion that "1.5 is stable and offers terrific user experience". Terrific user experience for 6 months maybe.
As a developer, If I leave behind a 1.5 version of the app, I will definitely be expected to support it as well. That is, if there is a bug, I will need to update my 1.6+ version as well as my 1.5+ version and all other versions that cannot be upgraded. Additionally, if this app makes use of 3rd party services such as let's say Facebook, twitter, Google's own services, or my own web service, etc - and those services change something in the protocol that I must also change in my app, I will need to update that 1.5 app as well. What about changes to the platform itself? Any single change to the main app that affects the functionality of the app will need to be propagated to all versions. It can get costly very fast.
It would probably be better idea to make sure the app is backwards compatibile and that one version is always updated. However, even that can also get very messy, specially if the app lasts for a substantial period of time and it spans multiple OS versions (MS has a lot of fun supporting Windows' backwards-compatability) .
It would all be easier if most users had the choice to upgrade to the latest stable release of the platform if the hardware supports it. But for that, we would need manufacturers and carriers to stop dicking around wouldn't we ..