"He's the Riddler!"
"He's going to take over as the Joker!" (Seriously, Google "Joseph Gordon-Levitt Heath Ledger" and tell us you couldn't see it happening).
None of them seemed to pan out - the Joker rumor, especially, was promptly shot down by Nolan himself. However, that doesn't mean Gordon-Levitt won't be heading to Gotham.
According to a Deadline report, Gordon-Levitt is in talks for an as-yet-unspecified role in "The Dark Knight Rises." The fanboy rumor machine is now in high gear, dredging up the old Riddler rumor and even suggesting that he could be Hugo Strange - a deranged, Batman-obsessed psychologist who hijacks the cowl for a brief time.
Incidentally, Strange was the role everyone was convinced Tom Hardy had locked down before Nolan revealed he would actually be playing Bane. We await word from the puppet master himself, but adding Gordon Levitt, Anne Hathaway, and Hardy to a cast that already includes Christian Bale, Gary Oldman, and Michael Caine seriously ups the ante for "Rises."