What they're trying to set up is a DC Universe franchise, and there's no way they'd do that without Batman being an ongoing part of it.
I agree, but I think they can do that with the new Batman appearing only in team movies, rather than investing in a new series for him.
Along those lines, if they are getting a brand-new Batman for the role, they could veer a little more in the direction of character actor rather than leading man, if he doesn't have to star in his own movies.
RDJ was paid 50 million for the first Avengers, and will like get more for the sequels. But Marvel Studios apparently thinks he is worth the investment since they just signed him for two sequels.
Since Marvel Studios has the massive Disney empire backing them, money shouldn't be an issue for them.
Warner Bros. ain't exactly a penny-ante operation, either.