The Q3 has already been released. I went to a pre-release showing of the car last week and Audi dealers are already taking orders. I doubt if there will be a Q4. The range will be Q3, Q5 and Q7. The 5 and 7 are, of course, already available.
As far as the A3 is concerned it will look a bit different to the existing 8P but it will be much the same size and still have 3 or 5 door and 4 wheels!! Most of the major changes will be on the inside rather than the out with the pop-up screen for the radio and DIS, different style steering wheel, DIS controls on the steering wheel, possibly an electronic handbrake (the Q3 has one), different style of radio that will take SD cards. A lot of it will be similar to the A1 and was on the Q3.