Jack will get his sword back
The Samurai Jack premiere, "XCII," drops viewers right into battle. As quickly as a giant robot beetle army circles a mother and two children, Jack makes his heroic entrance, mowing them down with a spike-wheeled motorcycle and blowing them all away with guns and explosives. Our hero now sports a beard and armor, and it's a terrific reference to the climax of the show's original pilot film, in which Jack took out an army of the mechanical bugs on his own.
But one thing's obviously missing, and Scaramouche, the musically minded assassin Jack faces later in the episode, points it out: "Wait, back off, Beardsley. Where. Is. Your. Sword?"
We still don't know. Jack's sword, forged by the gods Odin, Ra, and Vishnu, went missing at some point after Season 4 ended and before Jack grew his hair and beard out. A flashback tells us he dropped it down a shaft in a cave, which presents a problem for a couple reasons: 1) The sword's the only weapon that can kill Aku, as cuts from its blade make it extremely difficult for him to regenerate. 2) The sword and Jack are tied together by a blood pact, and its power comes from Jack's father, who first used it to defeat and entrap Aku. It's not quite the same as the connection between Thor and Mjolnir, but the sword is Jack's weapon, first and foremost, to the point where in the (non-canonical) Samurai Jack comic series written by Jim Zub, Jack magically pulled the sword out of his chest to block an attack from Aku. As Jack's mom says in one of the comic's flashbacks, "This blade cannot falter as long as your will is strong and your cause is just."