Not quite the same as Apple
While Apple do stop support on older models, I am not sure they can be directly compared.
So far, with the iPhone and iPod touch, Apple have supported two versions of the hardware at any given time. When the iPhone 3G came out, they carried on supporting the iPhone. When the 3GS came out, they stopped supporting the iPhone. When the 4 came out, they stopped supporting the 3G.
As such, each phone has been supported by new OS releases for about two years.
As I understand it, HP is now saying only new users will get Web OS 2.0. Existing users won't.
This, I think, could backfire on HP. Developers on the iPhone know that, thanks in part to what I have said above and in part to Apple quite rigorously enforcing updates on users, that around 90% of users will be on the latest OS version, or at least a recent one. As such, they can code for those versions safe in the knowledge that 90% of iPhone/iPod Touch users will be able to run their app.
Doing things the way HP is is going to lead to many versions of the OS being available..