If you know which fleet is to lose a squadron, then it is reasonably easy to predict.
In essence - it won't be 617 or 120, since their being awarded their standards ahead of the required 25 years accumulated service for award of the same has saved them from disbandment in the past.
AOCs do attempt to interfere, but in the past 15 years or so have be confounded by the head of the AHB, who tells them that there is a policy on number plates, which was established by the Air Force Board, and that if they wish it to be changed, they will (a) have to write a new policy and (b) then get it through the Air Staff.
The usual account used for stating the influence of senior officers concerns the reformation of 25(F) on the F3 back in the late 80s, where it is often alleged that a member of the Air Staff brought it about because that was his old squadron, thus ensuring that 85 and 60 Sqns, which had (it was said by some) a better claim to being reformed, were left in the lurch.
This rather overlooks the fact that on the AHB list of seniority, 25 was way ahead of the other two units and that of the numberplates not in use at the time, it was the obvious candidate if the rules were to be followed.
Any new squadrons formed in future - unless we have an expansion of the service on the same scale as the late 1930s - will have their numberplate decided upon the following:
1. Seniority
2. Past history in the role.
3. Possession (or not) of a standard.
If a training unit is to be awarded a numberplate, though, then other factors apply and seniority is not key; had it beem 76(R) would have reformed using a different numberplate. Service as a reserve squadron does not count towards reckonable service and thus (to date) does not affect the calculation of seniority.