Sales per-device is irrelevant, IMO. If I sell 100 for 10 devices, it's better than selling 90 for 3 devices. It's not like I have to add one IF() condition for each new model in my code; merely that I have to plan for slower CPUs and different screen sizes and resolutions, and when I do so, it's for a whole group of similar devices.
However, I have a HTC MyTouch android phone that is still stuck in 1.6 land. I upgraded from 1.5 recently, but it was not the simplest process to do so. HTC doesn't really make it easy for phone owners to upgrade their phone OS. It's possible for me to use the CyanogenMod to upgrade my OS to 2.0, but not without lots of effort at the command line.
The current slew of 1.5/1.6 android devices out there right now will probably never be upgraded to 2.x mostly because the phone manufacturers rarely make it an easy process.
Usage stats from my app in April (somewhat unscientific but illustrates my point decently): iPhone 3G: 49 users iPhone 3GS: 48 users iPod Touch 2nd Gen 4 users iPod Touch 1st Gen 3 users iPhone Edge 2 users iPod touch 1 user iPad 1 user (might have been me...)