Be aware that booking just a few units and oversubscribing terminals will be over when the new interface is put in action, and flights that do not have terminal capacity even by 1 passenger, will be cancelled. At least that's what I understood from the video "new features in action" posted by martin.*
* In other words, you must be able to meet/process full capacity in the assigned private terminal for all passengers on a given flight that has that terminal assigned, or the flight will be cancelled. The "overage" of passengers will no longer be handled by AS standard handling. So it will be one or the other (private or AS), with full capacity required for a given flight.
Unless you are investing in 50,000+ passenger terminals, now it's not a good time to invest in terminals, or to buy 500-1000 people capacity if you operate multiple daily flights.
Btw I already see owners of terminals complaining, because nobody will be buying 2000-3000-5000 units anymore and their terminals and respective investments going south of the border (aka going down). I do not foresee much micro-management to be done by airlines to assign capacity to just one or two (or handful) of flights and check the bookings so the terminal is not oversubscribed.
I also see problem with people actually buying terminal capacity, because you will need to buy more just to assure your flights are covered, and you pay a flat fee for contracted capacity even if you do not use it.
So right now if your flights have 2,348 passengers per week at city ABC, you need to buy at least 2,600 passenger capacity from the terminal operator just to be on the safe side if your bookings increase by 10%. And you better watch market every day because if your competitor bankrupts and your bookings go up by 20% you will be out of capacity and your flights will start to be cancelled, creating heavy losses for you (lost revenue + obligatory penalty for cancelled bookings).
As I see it, people will be using less and less contracted terminals, leading to a fury of terminal owners who will be losing contracts. I predict most of the players will want to stay on the safe side and not run the risk of this happening, or if they buy overcapacity (e.g. 30% more than they actually require) they will ask terminal operators for reduced pricing to compensate for the overage, which of course terminal owners will not be much willing to do.