New Shimano Di2 Dura-Ace R9200 & Ultegra R8100

I don’t think that was ever in the cards, I think you had the wrong expectations here. Such a move was never in Shimano’s interest. They only do it for the TT shifters, because “redesigning them” for no reason would not be in Shimano’s interest. (I say for no reason, because the brake levers are separate and work just fine. And the shifter is electronic, doh!)