But does it mean anything? It seems likely, doesn't it?
Potential spoilers ahead, so be wary.
For a little bit of context, the word Thursday comes from the Old English word Þūnresdæg and Middle English Thuresday, which means "Thor's day," presumably from back when people actually believed in Thor and the other gods of Asgard. You could torture the title, then, to mean something close to "Thor's Day of Mourning" if that's what you wanted to do.
Thor: The Dark World is the second installment of the film series, which reportedly revolves heavily around the character's relationship with Odin, his father and the head of Asgard's pantheon of gods.
Not long ago, a rumor emerged that Odin would die in the film--a believable enough plot development not only because the idea of a father figure dying is strong motivation in any story but also because the first Thor film featured a brief glimpse at Odin's armory, which included the Infinity Gauntlet, the weapon of choice for the mad Titan Thanos.
Thanos, of course, appeared at the end of Marvel's The Avengers and is widely expected to appear in both Guardians of the Galaxy and The Avengers 2. And Loki--Thor's adopted brother who antagonized him in both the first film and in The Avengers--worked for Thanos in the latter. Even if rumors that Loki will see the light and become less villainous are true, the chances are good that returning home with Thor at the end of The Avengers may have provided Thanos's minions with an entry point into Asgard.
But as far as I can tell, if Loki is actually redeemed in the second movie, that's actually more reason for Odin to die than if he didn't--all that Loki has ever wanted is to be the Lord of Asgard, and with an earthbound love interest and responsibilities around the universe in The Avengers 2 coming on the horizon, Thor wouldn't seem to be an ideal choice to replace his father should he die. Could Loki get a happy ending that puts him in charge of Asgard and potentially puts that realm at odds with Thanos in the end? It feels right.