To get back on topic, there are a few curious details about this new game. First, some sites say it's an "epilogue" rather than a "sequel", and it should be noted that it's titled "FFIV The After" rather than "FFIV-2". Moreover, it supposedly takes place on the moon, but anyone who played the original game knows that the moon is pretty much barren apart from a few dungeons and that Hummingway village... So, can a fullblown adventure really take place there?
I may be reading too much into it, but perhaps this means that the game will be a sort of sidestory with a minimal story, and will be mostly focused on gameplay rather than plot, with Theodore exploring some random dungeons on the moon or something? Kinda like those bonus dungeon sequences from the FF ports on GBA. In that case, we wouldn't be missing much.