A report from The Independent (via Bleeding Cool) says Miller will "be meeting up with Zach [sic] in the next few days to go over the plans for the Superman film so things should be clearer after that." Miller apparently had no idea about the untitled movie's announcement, and definitely wasn't aware that it would be inspired by TDKR, so chances are this little get together could just be friendly conversation between colleagues. But given their past history, and the success they've had as a team, one has to consider the possibility that Snyder will want Miller to take a more active role.
It's important to note that the film is merely inspired by TDKR, not based on it as some have assumed. The story has an aging Bruce Wayne taking up the mantle of Batman one more time to save a dystopian version of Gotham City, with Superman working with the government to bring him down. It's completely a Batman-centered tale, and Snyder's film will be focused mainly on Superman. It's a proper Man of Steel sequel in that respect, with Batman introduced as a supporting character and a temporary rival. It's for that reason we likely won't see the film titled Superman vs. Batman as some predict, because it suggests equal billing.
Whatever the film will be titled, it's expected to open in 2015.
