The seating plans of the A3XX show the following classes:
Economy, main deck, 3-4-3, considerably wider than the 747's seats, and 2-4-2 on the upper deck.
Business, main deck, 2-4-2, also very nice, and 2-3-2 upper deck.
First class would be on the lower deck only, 2-2-2, behind the stairs, not in the nose.
Airbus has also considered, though I haven't seen any official material regarding, a high-density 3-5-3 eco. arrangement. This would be about as rare as 3-4-3 on 777s, I suspect.