Changes on The Moscone Center's calendar of events show that an unspecified "Corporate Event" that could be Apple's 2010 World Wide Developer Conference has been moved from June 28th - July 2nd to June 23rd - June 24th. Sun Microsystem's JavaOne Conference had been scheduled during that time frame, but that event is no longer on the calendar.
At issue is nothing more than trying to divine when and where Apple will hold the WWDC event before it's announced. The company often has the WWDC listed as a "Corporate Event" on Moscone's calendar before the event is officially announced, and when a "Corporate Event" for late June - which is in the middle of Apple's usual window for the event - appeared on the schedule in December of 2009, speculation began as to whether that might be WWDC 2010.
There is, of course, no guarantee that the "Corporate Event" currently listed for June 23rd and 24th is Apple's event, and it's important to note that the WWDC is usually held over the course four or five days, not the two days currently listed.
Accordingly, we're all in wait and see mode for WWDC until Apple announces it.
It is also worth emphasizing that the disappearance of Sun's JavaOne is an interesting development. The JavaOne event has been one of the world's premier Java-oriented events for some time, but Oracle bought Sun in April of 2009 for US$7.4 billion, and JavaOne might be subject to cancellation or other substantial changes.
Thanks to 9to5Mac for the heads up.