New iPhones are now obtainable, and so is the most recent version of iOS, which provides a host of new features worth looking at.
Apple has verified that the new software update will perform on any iPhone going back all the way to the iPhone 5s. For the iPad, anything from the iPad Air 1 or after and iPad mini 2 or later (including all iPad Pro models) will also be capable to run the new software. If you have a 6th-gen iPod touch kicking around, that one also receives the update.
If you have not updated still, it is simple to download the new version. Go to Settings> General> Software Update to start the process directly on the phone or tablet, or plug into a computer and open iTunes.