It strikes me that so far nobody posting on here actually has any knowledge regarding:
The numbers involved (I think 30 may be an over estimate)
The roles they will undertake in their respective HN (not all are flying posts)
The T&C attached to being considered for seedcorn (do you really think it hasn't occurred to the RAF that people will jump ship if they can easily do so!)
Therefore just about everything being written is speculation, but I guess that is most of what pprune is about!!
I will offer one fact, and then some speculations of my own. Fact - some of the people going overseas as seedcorn are WSOs. One has to wonder why? The WSO trade is dead. We are not recruiting any more, the training school is shut (indeed some of the WSOs still going through training were recently made redundant as part of the SDSR - needless to say, it didn't make the headlines in the way the sacking of baby trainee pilots did) and the pool of remaining WSOs is quite small and shrinking (over the past 5-10 years most WSOs have been recruited on short service commissions). Therefore, if we are to buy a new MPA in a few years time, with a projected life of 25-30 years, how do we plan to put WSOs in the back of it? Recruit off the high street and put them through RN Observer training? Or do we not plan to have officers in the back of any future MPA -indeed, WHY SHOULD WE? Or will the next generation of UK MPA be run by the RN, in which case, what price RAF seedcorn!
So, if we don't plan to man any future MPA with WSOs, why retain them as seedcorn? All I can suggest is that they will be used as instructors, training the next generation of TACOs, whatever rank and trade they might happen to be!
Speculating now - I can't see HN wanting to take people on indefinitely, don't forget, these aren't exchange posts, we have no MPA slots of our own to offer in "exchange". They are doing us a favour, and hold all the cards in the deal. Also I would expect the RAF to be reluctant to leave people overseas indefinitely, the RAF would no doubt be concerned about the impact on peoples careers! The RAF is strange like that!
For what it is worth, I personally consider the seedcorn concept to be something of a sop/figleaf, so the minister can imply the capability can be regenerated at short notice. I would expect the "seedcorn" to slowly whither on the vine with the passage of time, with anyone who returns, gets promoted, etc not being replaced - but that is my speculation!!