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/.
Apple's next event is happening Monday, March 21st, when we're expecting it to unveil a new iPhone, a new iPad, and likely a bit more. The announcements are shaping up to be a sequel to those made at Apple's last event, held six months ago. There, Apple announced the iPhone 6S, iPad Pro, an expansion of Apple Watch designs, and updates to iOS. This month, picture all of that repeated, but smaller.