I would love to see a World's Finest movie first. It would be a great way to build up to a JL film. In way I think you need Superman or Batman to set up there world, introduce us. I know that superman is coming out next summer and I suppose be kinda like what Ironman did for marvel giving us our first steps into a connecting DC film universe.
I know it's not going to happen but WB will follow the money like Marvel has done successfully (as far as story's go I think they've lacked other than the first Iron Man). I would hope that WB would go for quality and a strong build up then just pumping them out.(hopefully learning from the mistakes of the green lantern movie) I think WB will fail if they follow the "marvel plan." First marvel established there universe over what a 4 year span. I don't think that WB should expect to do it faster, plus we are way more saturated with superhero moves then we have ever have been before. (Don't get wrong it's an exciting time to be a comic book fan)
WB has to do something that sets them apart. A JL movie will make a lot money just off of novelty like the Avengers cashed in on. I consider myself I guess more of DC fan I don't know (with exception to Spider-man, X-men, Dare Devil, Iron man, Hulk lol) I truely enjoyed the Avengers, I've seen it multiple times but I know for me the novelty of all those great heros on the screen plus non-stop action is what sold it. (Which is great that's what they intended I think) Like I said WB has to do there own thing.