FFP,
Sounds like you are in the same boat as me - option point in 2014 and waiting to hear the outcome of the review. However, we did ask that very question at a briefing and were told that wouldn't happen.
I have to say that part of me does have a degree of sympathy for the 4 man pensions team working down in MB at the moment, if for no other reason than their names and pictures plastered on the web as being the architects of the coming train crash. That said, I'm pretty sure (well hope at least) that their role is not only to redefine military pensions, but also to protect service personnel to the best of their ability; we all know that given half a chance the Treasury would cancel all our pensions and charge us to come to work.
To avoid a mass exodus to the point that threatens the operational effectiveness, possibly even the viability, of the military as a whole, there will have to be some sort of transitional arrangement. So assuming that if you fall into the bracket of being able to draw an IP before 2015 but stay on, I would hope that the promise of keeping what you have already accrued would mean that if you stayed in past 2015, you would be able to draw whatever you had earned up to that point with the rest being paid under some sort of transitional arrangements - possibly in the same way they have increased the state pension age - i.e. retirement at 55 for one age bracket, 56 for another, 57 for a third etc.