Why do people think a new iPhone is coming this summer?

MacRumors has a story up with a photo of an alleged iPhone 6 case from a 3rd party case maker. Some posters there are speculating all these recent leaks mean a summer launch for the new iPhone. But iOS 8 hasn't been announced yet. Don't we need beta testing of iOS 8 before we get a new phone? When the iPhone 4 was launched in June the neat version of iOS 4 has been announced in April. If Apple was planning to announce new iPhones at WWDC wouldn't iOS 8 beta have been released already?