As of now, the deadline for filing 2010 Form 706 is September 17, 2011. The due date for filing Form 8939, as mentioned above, is November 15, 2011. Both the 706 and 8939 have only been issued in draft form.
The AICPA is recommending that the IRS extend both of these due dates and make them due 90 days after issuance of the final form, whichever is released last. The AICPA is also hoping that the IRS will issue procedures for estates to obtain a six month extension to file Form 8939. Stay tuned for any updates!