It looks like a sure thing that SpeedGrade is a part of Production Premium CS6; however, I don’t know if it will be available as a standalone application. Adobe SpeedGrade is based on a new version that Iridas was developing (and had not made available to the public) prior to Adobe’s acquisition of it.
There will be no Dynamic Link or “deep” integration with other Production Premium applications – yet. Deeper integration is likely on its way, but not in time for CS6.
The Premiere Pro CS6 integration for SpeedGrade will be a separate menu item that says “Export to SpeedGrade.” This is a one-way export intended for use once the edit is complete and you are ready for finish grading.
It should be ready with the rest of Production Premium CS6 in time for the NAB Show in April, which should be huge for Adobe on the whole.