ModMyi reports that Apple has booked the same conference center where the company announced the three previous versions of the iPhone for June 22, 2010. Looks like the perfect time to announce the fourth generation iPhone hardware. It also reports about the "a late-breaking tip from Flurry Analytics suggested the possible existence of a Verizon iPhone being used in the US in recent days."
[update: My apologies, the headline mistakenly said May when it should have said June. I also added "Rumor" as these reports are unverified.]
Tip: MacDailyNews via ModMyi