@ Holy man,
your theory is not totally correct I am afraid. You forgot to take into account the following:
1) 1000 pilots is more or less correct. 60% captain/40% FO
2) On the large cabin fleets the ratio is even higher, as they fly a lot with reinforced crews with 2 Capt and 1 FO
3) Of these 1000 pilots, a big number are young FOs, needing hours before becoming captain. Besides that there still is a 50% fail rate in the upgrades.
4) With the new seniority system, people will get seatlocked for longer. This could mean a faster tranfer to large cabin as well.
5) Not all pilots are interested in flying long haul.
6) In order to transfer to e.g. the 7X, long haul experience and other things will be taken into account as well.
7) Netjets crews at 6 pilots per aircraft. (bit higher on long haul)
So when you take all this into acount I think it might happen just a bit faster than your prediction.
People who started 1.5 years ago might expect a large cabin airplane within 3 years to come.
People starting now, could expect ( if experienced enough) a large cabin after 5 to 6 years.
( These figures come from an experienced netjets pilot, they are not mine...)