Did a lot of people jump to the D7 from the D8? I didn't and waited for the M1.
I don't know the US situation back then, some of the oldie DAT-heads can probably tell more.
Over in Europe, these machines retailed for $1000 back then, and very few tapers could afford a D7 or D8 in the first place.
I had a D7 as a loaner back in 1994-95, and I didn't see any major reason shelling out money on the D8 when it came, being so similar.
I recall the D7 being a badass battery hog, I don't know if the D8 improved in that aspect.
Maybe for US tapers who were still on analogue, the pricepoint of the D8 was low enough to make a move at the time?!