Sorry, not got any new info, first I have heard of it. Just a couple of thoughts from a bear with a very small brain, if it does happen. First of all ironic that MOD have just introduced a system of "bungs", sorry financial incentives, for aircrew to stay just to have prospect of Treasury puting in place great incentive for people (all trades) NOT TO STAY! Loss/tax of gratuity worth £60,000 plus, depending on rank/time in job, big incentive not to stay to 55. Secondly, if tax/scrap of gratuity was introduced for people already serving, as opposed to new entrants, would you have legal grounds to sue MOD, on basis tax free gratuity was one of reasons for joining/remaining and part of your terms of service (European court here we come again!!)?
That nice Mr Brown/Treasury trying to claw money in any way they can without touching the sacred cow of current income tax rates!!