Given the money that has to be spent on the manufacturing of the coaches, it is economically not feasible to quickly change over to any new technology that comes along. Again, here also, the transition has to be gradual for making the best utilization of existing rakes while gradually switching to a new set with minimal cost overhead.
Tha said, IR is definitely going too slow with the transition to LHB. The end of 2016 deadline will definitely not be met. IR needs more focus on solving the LHB design issues and bringing down the cost. Sorry for the long answers. :)