Doesn't mean anything - it's done all the time by big studios. They enlist writers to do another instalment (in this case, it's another entry in the DCEU), even before they hear about the picture's critical reception. This was the same case with Orci and Kurtzman being enlisted to write TASM3 months prior to TASM2's release. We all know how that turned out.
Time will only tell if it was the right decision. And if the film is received negatively/mixed, you can bet your butt that WB will be changing their game plan (either a new writer, director, etc.).