The equals sign means is equal to. It is telling us that one thing equates to another; that they are the same.
The iPhone 4 is the most recent iPhone to be discontinued from the iOS Update cycle. It did not receive the iOS 8 update, so it's final software version is iOS 7.1.2. You can update to this version through iTunes, or download it from an IPSW repository like this website: https://ipsw.me/.
iPhone 6S or iPhone 7 (2015) We'll surely see a new a new iPhone in 2015 and it'll probably be the 6S. If it turns out to be the iPhone 7 Apple will have broken with its conventions from the last few years. Don't forget to check out iPhone 6S: everything we think we know.