Nothing official has been announced by Paramount or Marvel yet but Amazon Germany have put up Iron Man 2 with a pre-order date of 7th October.
The movie was released in cinemas worldwide a week before in the US so it's possible that the same will happen with the DVD/Blu-Ray release as well. However, it's fair to assume that if this date is accurate we can all expect to be able to own the movie in the first few weeks of this coming October!
The German shoping site also lists a limited edition Steelbook version of Iron Man 2.