As you can read from the description of the chart at the top, this is with BiS t9 in 3.3 mechanics and t10 2pc and 4pc bonuses.
The link the poster gave to the previous simcraft(using PP values from shadowpriest.com and 3.3 mechanics), does not compare to any other classes, but comparing that dps to that from the chart, it is a 1k dps increase.
The original dps gain between 3.2.2 and 3.3(minus scaling factors) can be found here.
From that I'm seeing us moving from the bottom of the meters to being only behind balance druids (the class that's above us currently on the bottom of meters now lol). Interesting change of things. I hope that's true and we are buffed that high.
A large part of that is the T10 4p bonus, which is absolutely amazing. You're talking about a 17% gain to your top DPS spell. It's quite possible that Shadow will be one of the top DPS with that bonus. Otherwise you're looking at about a 10-15% gain to a class that's already 20% or more behind the pack.