It's possible, but I doubt it. WB today estimated it would end up around $520 M domestically.
Today's movies run on a reverse exponential curve (for lack of the correct mathematical term). Next weekend's gross should run around $16-18 M. The following weekend around $8-10 M. Probably stays at $10 M the next (Labor Day weekend). But $5 M or less every weekend after that. By my estimate that puts it around $510 M the weekend after Labor Day, two months after its release (counting weekday numbers). I could see an additional $40 M for the rest of its run (maybe another 6 weeks) but I can't say it's definite.
Put another way, TDK's box office has mirrored Pirates 2: Dead Man's Chest (albeit at an accelerated rate) in the daily box office day over day totals. At this point DMC had made $350 M, putting TDK 25% ahead of DMC thusfar. DMC made an additional $75 M after this point of its release, so applying an additional 25% to that total yields $95 M for TDK, with a final total of $536 M. And both had a holiday weekend midway through its release (July 4 for DMC, Labor Day for the TDK).
I'm expecting someone to say that DMC did not have the word of mouth, super hype, and critical acclaim that TDK has. While that is definitely true (TDK is twice the film DMC was), the numbers do not lie. TDK is making more money, faster, but it is still dropping at a similar rate.
Also, comparing any movie's run with Titanic's is completely unfair. TDK will not be making $100+ M a month for four months.