It makes plenty of sense. The two have been involved in hundreds of things before, including a cartoon series and a few animated movies. And with Marvel beginning Phase II with their highly successful team ups, DC needs to catch up.
Let's just hope that this opens up the way for the Justice League movie we've been waiting for. They've been saying it's happening for years now, but it never has.
Because superhero movies have finally hit their stride after decades of sub-par adaptations. Sure, we could have had Adam West in a Superman movie, but I don't know about anyone else, but that doesn't sound very epic.
Besides, the cost for having a collaboration of this magnitude would have to match the profit of the movie. A Superman/Batman failure movie in the 80's or 90's could have severely damaged the production company.
DC has been super disappointing with their movies lately (besides the Dark Knight series.) Man of Steel was a little better, and hopefully this won't disappoint. Pretty excited for this, but also a little nervous.