Having just checked the WWE Home Video schedule that we have access to, it appears the entry for the SummerSlam 2011 Blu-ray has been removed.
This does NOT confirm it has been cancelled and it does seem unusual. However, keep in mind when this occurred for Capitol Punishment and Money in the Bank those two titles did not make it to Blu-ray.
A planned 2-Disc DVD edition of SummerSlam was also dropped from the same schedule recently
Our information relates only to North America, and we know SummerSlam is available to pre-order on Blu-ray in the United Kingdom right now.