Don't worry, iOS 9.2 has big improvements to A5 devices, I think it will improve the user experience and make it better. Don't give up on iPad 2, it's amazing that an iPad that old would get iOS 9 or even 8 but I'm glad they at least support it, the iPad mini has the same problems and I think apple won't like having 48% of their customers sad, the iPad 2 is still has the highest market share over all iPads (20%) and the iPad mini 1 has also the second highest market share (18%). Just don't worry about it.