I don't know how I feel about this. On one hand, CW had done really well with those properties and they would be validated further by merging those universes. But on the other hand I'm afraid that merger will put serious restrictions on CW branch of it. Heck, I doubt we would be even getting Flash tv show at all if the universe would be shared from day 1.
The best case scenario would be for DC/WB to just say "fuck it, do whatever is awesome" and allow merger for movie, while still allowing CW to do whatever they want on small screen, including allowing Arrow to steal everything from Batman
. I hope that since they already are putting shows on multiple networks it means they don't have a hard-on for keeping everything tidy and shared, the way Marvel does. DC's aproach to animation is exactly what needs to happen in live action too.