You can safely take this with a fairly large grain of salt, but according to the latest rumor surrounding the HTC EVO 4G LTE, the device could hit store shelves as early as Friday, May 18 – much earlier than the June 6 date that was thrown around earlier.
A May 18 release date would break the mold that Sprint has set of releasing devices on Sundays. However, Sprint has made exceptions in the past for notable phones; for example, the original EVO 4G was also released on a Friday.
Additionally, HTC has said that the EVO 4G LTE can basically be considered a rebranded (and somewhat redesigned) HTC One X, which is set to hit AT&T on May 6. The HTC One S is also coming to T-Mobile on April 25, so HTC might want Sprint to release the device a bit earlier in the year than previous EVOs.
In any case, preoders are all set to begin on May 7, and that's definitely not a rumor.[PhoneDog]
Update 4/23: This rumor has supposedly been corroborated by another source inside Sprint, although it's still just a rumor at this point. (Thanks, John!)