If you read through the report [ok it's 99 pages so maybe not], you will see there are quite a few crude estimations in place. Simply look at how they forecast how many A380 freighter versions will be sold over a 20-year period....by looking at the deliveries of 747s made, looking at how many of these were freighters (9.9%) and then applying this to the A380 ... yeah ok!
Interestingly, with the 747Adv in the near-term pipeline, this report also points that [if you read between what they are saying about the A380], the 747Adv will only sell around 300 aircraft....that's 12 aircraft produced PER year or one / month. Not too much really!
Cheers
CP