While Sprint has yet to announce a release date for RIM’s Wi-Fi-only BlackBerry PlayBook or the WiMAX-enabled BlackBerry 4G PlayBook, the former was recently rumored to be set for a May 8th launch. According to a purported communication sent from Sprint to dealers, however, the launch may have been pushed back. “The launch of the BlackBerry PlayBook Tablet has been delayed for all Dealers,” the supposed note from Sprint states. “The new launch date will be communicated as soon as it is available.” The cause of the delay is not specified, though initial sales are believed by some analysts to be exceeding expectations, which may have caused supply constraints. Others believe the large quantities of Apple iPad 2 units being produced by Chinese manufacturers are causing manufacturing delays for various Apple competitors. Then again, Sprint may be waiting for an imminent software update from RIM that will add various much needed functionality currently missing from the PlayBook, such as an email client and BlackBerry Messenger support.