The problem that Apple is avoiding though is having a bad experience because you have an outdated OS - this occurs on the desktop with OSX as well. Because older OS won't handle newer software gracefully they just "Force" the upgrade. Not saying I agree with it, but that's the assumed policy.
A 3-5 year old phone should do the job just fine.
I gave an old iPod Touch 2nd gen to a relative and was super annoyed that a 2 year old device doesn't have Skype anymore. I'm pretty sure it had at some point but since the device is stuck on iOS 4.2.1 I can't find the old Skype versions on AppStore anymore.