If you go by just expectations alone iphone 5 is already super hit even before an announcement of the phone from apple. After the antenna gate of Apple iphone 4, there is a huge expectation on the next version of iphone, and going by Apple's plan in the last few years we should have a new release of iPhone in June-July 2011. But then again going by the tone steve jobs set in ipad 2 launch we may not see a huge change in hardware from iPhone 4 except the antenna.
Another question is whether Apple will call the new phone another version of iPhone 4 like 3GS for 3g. With not many new enhancements a subversion of iPhone 4 will be the correct approach but again they may want to completely forget the iPhone 4 episode and jump to iPhone 5. With the new a5 processor confirmed to be available for next version iPhone, it is most likely to be christened iPhone 5.
Another factor in the recent months is japan earth quake and Nuclear disaster which could push Apple's schedule at least by few weeks if not by few months. And Apple's have said they dont have any roadmaps from Apple for new product line, but again considering that iPhone 5 may not be much different from iPhone 4 and could be a more refined product, the information leak possibility is also reduced.
So lets wait and see if we get to see the new iPhone 5 this summer.
iPhone 5 may be delayed because of many reasons