It should remain at least until the current children are 18 for existing claimants
I suspect that will be the case provided you continue to meet the 'requirements', which will get 'tighter', more controlled and more 'tested'.
However, on a tangent, what about continued payments for those children of servicemen/women made compulsory redundant....? No more different than removing CEA from someone still serving who doesn't actually need it because they never move units but still claim the allowance ....