Today, Microsoft announced that over the next few days, it will be rolling out a new version of Skype for Android that's optimized for older devices. More specifically, it's aimed at devices running between Android 4.0.3 (Ice Cream Sandwich) and Android 5.1 (Lollipop).
Microsoft says that the new version is "lighter on both disk and memory consumption", meaning that the app will be faster and provide better video call quality. Due to the app needing less resources, it will also provide better performance in suboptimal network conditions. Obviously, this all results in a better experience on older and lower end devices, and in regions like emerging markets where cellular networks are less developed.
According to Google's latest Android usage report on February 5, 42% of all Google Play devices are running on a version of the OS between 4.0.3 and 5.1, so it makes sense for Microsoft to want to provide a better experience to these users. An additional 0.3% are still on 2.3.x Gingerbread; however, anything earlier than 4.0.3 is officially unsupported by Google Play Services.
If you're already using Skype on your device, you should see this update automatically over the next few days. If you want to install it manually, you can find it on the Play Store here.