I must say, Batman is nice, and it'll propably sell well, but I just don't find it to be appealing. Pirates of the Carribean would be nice as a theme, but there would be certain restrictions. For instance, Lego would give us ships and characters from the movies. Which is okay. But it also means that Lego's creativity is held back by the license. If they'd just make pirates again, they could do whatever they wanted to because there would be no license terms. Plus, we likely wouldn't see 'normal' pirates for a while (like we haven't seen a 'normal' space theme ever since Lego got the Star Wars license)
So the license would be appealing for some, and would likely sell better, but I'd still prefer the good old pirate sets to return ;-)