I gained the impression that there were quite a few middle-ranking officers and SNOs who stayed in past their IP point because their kids were in receipt of BSA. This is a small but significant cadre of all 3 Services and, if the incentive to stay in beyond 22/38 (or whatever it is now) whilst raising a family is removed, then many will walk out.
Someone mentioned a mass PVR on this thread or another. Although the powers-that-be could deal with this under QRs by extending notice periods, the political fall-out could not be contained. If a significant percentage applied to PVR (say above 10%) then this would generate much press coverage and Parliamentary debate - perhaps leading to a vote of confidence in Browne (or whichever other nonentity it is by then).