The move only applies to new releases from Warner Brothers, but don’t be surprised if the movie rental company segways this policy for other movie studios as well.
And though this sounds like a terrible deal for the company from a consumer standpoint (does anybody really want to wait for anything?), it’s actually not that bad.
The trade-off here for Netflix, is the delay in renting new releases until 28 days after they’ve gone on sale allows them greater access to stream Warner Brothers’s content. I suspect Netflix is looking at the greater endgame and realizes their future is in streaming online content and not physical DVD rentals.