It seems that there is little bit confusion in this matter,since we are following a system of segregation of pensioners based on their date of retirement under BPS/JN wise.Certainly it may be there till a formula is agreed and finalised.
Tapering DA formula may not be continued on revision of pension.Once a revision of Basic Pension is made on merger of certain points (let it be 6352 or more)naturally only single uniform rate of DR can be applied further(And not any different rate to different categories based on retirement date as doing right now,including tapered rate)
Example on Pension revision in RBI is before us,though they have carried up to 2012 with merger of CPI 4440 points,only.Yes,they have already extended 100% DA earlier so this question of tapering formula, does not arise there.But single uniform DA rate is followed for all pensioners up to 2012.
Only on account of this aspect,segregation is made for us,based on merged CPI points of 600-1148-1684- ... and so on up to 6352 points with different DR rates including tapered DA.
While enhancing basic pension of of a retiree under Vth ,VIth or VIIth or VIII BPS /JN to the level of 11th or 12 th BPS/JN on a uniform level,there may be only one uniform rate of DR further.
Or else the very basic concept of Revision of Pension may be defeated.That is not the Revision of Pension, the pensioners demand.Further segregation may not be/cannot be there with different DR structure.