Samsung Galaxy S2
The Samsung Galaxy S2 still hasn't received Android 4.2, or Android 4.3 for that matter, and given its age, we doubt that Samsung is going to roll out any more updates for this once mainstream smartphone. Indeed, the phone is still being sold through some outlets, same goes for many of these phones, so buyers will want to keep this in mind before picking one up.
Android 4.4 KitKat isn't coming to the Samsung Galaxy S2, no matter how bad owners want it. Instead, users will have to rely on the development community for support.