The problem with Android Lollipop [for developers] is [still] the "android fragmentation" problem, which Google is trying to address with its Android One program. Lollipop has 5000 new API's, but developers have to program to the lowest common denominator, which is probably pre-4.0.
This is in contrast to Apple. Most devices get upgraded to the latest iOS in short order [3-6 mos]. IIRC, an author writing an iOS developers' book stripped all pre-iOS8 from it, because he felt that iOS8 was just so much better. Whether he's right or wrong doesn't matter as much as the fact that he can do it because of the iOS upgrade cycle. This makes iOS development much easier than Android development.
The latest Linux runs quite well on older devices. So should Android. This is just like a PC game that, during install, speed tests the machine and backs off on things like resolution, anti-aliasing, etc. to make it run smoothly.
Android One needs even more teeth:
- Vendors _must_ upgrade old devices [even at a loss] unless they can prove [to Google] that it won't run due to memory, etc.
- Vendors shouldn't force people to upgrade their device just to get the latest Android, just because the vendor wants to force this by refusing to upgrade Android on "last year's device".
I have a Galaxy S3 and Samsung has upgraded it every six months. I really like the fact that they're not forcing me to upgrade the device just to get the latest/best Android OS. As as result, they've got my loyalty. When I do [eventually] upgrade my device [at a time of my choosing], Samsung's firmware upgrade policy will be a major factor in my staying with them.
If Google can't get vendors to cooperate [even better] on this, it should offer backports of Lollipop [API's] to older versions via Google Play. This helps consumers with older devices, Android developers, Google, and even the [recalcitrant] vendors [even though they might vehemently disagree].