It's not about the tone, it's about the quality of the movies. Just produce good movies then whatever tone they choose will be perfect.
Look at Batman Begins and TDK. Two high quality movies with a tone suited for them. TDKR and MOS used the same tone, but the quality was subpar, so the whole movies fell apart.
As long as WB is at least trying to make quality movies, I'm fine with it and on their side. Just remove Snyder for someone with a little more filmmaking skills who can produce high quality movies and their Superman films can be as gritty and grounded and unsupermany as they want.
That said, I'm curious about the line up, hoping that out of the 10 movies they announced at least 4 of them won't be Batman movies. Which raises the questions which characters will get solo movies, who will provide the scripts and who will direct it