For HFM to discontinue the HE-400 and HE-500, Dr. Fang must have high confidence that his new creations will eclipse them in terms of performance. I personally love my EQ'd HE-400 through the Asgard 2, but I don't like it nearly as much without EQ. Too much treble, mainly.
They made a similar move with the new IEM line.
I still didn't make the move, I love the RE-262 too much (bargain), plus they remind me of my (long) departed HE-500 (mid-centric).