Both "WrestleMania 28" and "WWE: The Best of WCW Clash of the Champions" are listed as pre-order items on WWE.com, set to release on both DVD and Blu-Ray. While WWE.com has been non-specific, according to Amazon.com, both films have a definite release date for this month.
"WrestleMania 28", featuring John Cena vs The Rock and Triple H vs the Undertaker inside Hell in a Cell, is available May 8, 2012. As of now there is no information on a "collector's edition", but WWE will usually put one out after the regular version has had time to sell.
"WWE: The Best of WCW Clash of the Champions" is available later this month, on May 22nd. The DVD is a 3-disc set (2 on Blu-Ray) and will be hosted by the "American Dream" Dusty Rhodes. The box art features Ric Flair and Sting in one of their first classic matches. You can see a preview video for the film on Amazon.