Yes, it's iCloud

In an announcement that reads like something out of the Apple rumor mill, Apple has announced that it will be announcing iCloud at the June 6th keynote.

CUPERTINO, California—May 31, 2011—Apple® CEO Steve Jobs and a team of Apple executives will kick off the company’s annual Worldwide Developers Conference (WWDC) with a keynote address on Monday, June 6 at 10:00 a.m. At the keynote, Apple will unveil its next generation software - Lion, the eighth major release of Mac OS® X; iOS 5, the next version of Apple’s advanced mobile operating system which powers the iPad®, iPhone® and iPod touch®; and iCloud®, Apple’s upcoming cloud services offering.

Apple announcing something in this way seems very strange, I can't recall another time that they've unveiled a new product in this way.

Source: Apple