A while back, Tony Daniel was to be replaced by Ed Benes to do Detective Comics #10-12, which apparently did not happen. Since Ed Benes is doing Batgirl , Tony Daniel will continue doing Detective Comics. He will also be doing Detective Comics #0 making him stay extra longer on the comic book. Apparently, Daniel needs a break. So, he is also up to do Justice League for two issues as a guest artist starting in October. I guess this is a test to see if the fans will like his artwork.
Source- Comiclist
Kristina