WWE is finalizing plans for the upcoming 1,000th episode of RAW. Big names already confirmed include The Rock, Brock Lesnar, Mick Foley, Bret Hart and a DX reunion (Shawn Michaels and Triple H).
There will likely also be appearances from Vince and Stephanie McMahon, with Shane McMahon being a long-shot and Linda McMahon considered unlikely, due to her ongoing Senate campaign and their efforts to distance her from the WWE product. There will also be a slew of "2nd tier" legends appearing (the usual suspects).
As for the Undertaker, it will depend on whether WWE plans for him to work SummerSlam. The show is so stacked already that it would not make sense to bring him in unless they will be building towards an upcoming match.
With the audience of RAW's 1,000th episode expected to be one of the largest of the year, WWE will capitalize on this by making Brock Lesnar vs. Triple H official for SummerSlam.
(Source: Wrestling Observer Newsletter)