You can't find a date because it hasn't been announced. No one knows when it's going to be announced. Keep visting the DPB site and you'll see it when it's announced. You could also subscribe to the XNA Team Blog. Your second question won't be answerable until they announce the contest. Assuming it's the same as the first one, you can submit anything you want. You know what they say about assuming though... :)

As previously said nothing has been announced but since we just had a warm-up challenge it seems quite reasonable that it was warming is up for something.

You dont have to wait for the announcement anyway.... get coding... (assuming like last year that only the warm up had the 'theme' and the final was anything goes')

THE FINAL HAD BETTER BE ANYTHING GOES!  lol  I've been working on my game for a long time now...