Apple will most likely launch the second major update to iOS 8 iOS 8.2 that has been testing since last November 18, 2014. Finally after five betas, the final version and would be ready to reach all compatible devices. iOS 8.2 will also include improvements in the functioning and stability of the operating system for iDevices, improvements in health applications to perfectly fit the data you receive from Apple Watch as the typical error correction, you can not miss any update, not only iOS but also from any application.
As to fox errors encountered from time to time, this update will fix some problems but not all, and certainly new bugs appear, as usual at each update of iOS. Toward raising the operating speed of older devices most likely not reach this update. Maybe Apple once already forgotten the older devices that are doomed to disappear with iOS 9 such as the iPad 2 and iPhone 4s.