I have just phoned customer services at Duxford with this question. I was advised that it is intended that the grandstand will be situated in front of the British Airliners collection. The person I spoke with wasn't sure of seat numbers, but thought it will be about 500 for this first time. There will be no standing crowd in front of the grandstand. Seats are not reservable, so if you are with a group and arrive once all other seats are taken you may have to split up i.e. seat 'allocation' on the day is first come first served and subject to your own choice based on what is available.
I also asked about siting of the Friends of IWM enclosure. I was advised initially that they thought that this would be in the same area as the previous Friends of Duxford, but there may also be a slight change in the offing by moving the Friends of IWM area further towards the centre of the crowd line, nearer to the control tower.
Brian