I have mixed feelings on this. I will DEFINITELY miss Geoff Johns if he's 86d as he's my favorite writer of all time but the rest have been Luke-warm at best for me recently. Snyder's Justice League was only about a 6 or 7 out of 10 stars IMO while Morrison and King haven't written anything that's really excited me in a while although I haven't read a whole lot of King's recent work.
As for newer or less popular writers being on DC's more popular books(i.e. Batman, Justice League, Flash, etc.), I can see sales slipping with some exceptions of a good writer/book match. Most of these big name writers do have some very loyal fans that will drop the books as soon as a new writer takes over and follow the big name writers to whatever book/comic company they go to next.