He wouldn't have saved the Rebels, meaning Luke, after jumping into the pit when Vader revealed he was his father, would not hold out forever and died. Yoda could do nothing, and just died on Dagobah.Vader would sense it, and be sad because his son was dead, and because he could no longer kill Palpatine. Palpatine would also be pissed because he wanted to replace Vader with Luke. Leia and Chewie would remain prisoners, unable OT be broken out because they are of so high value to the Empire. Han would eventually be saved by the Rebels. Knowing that torturing Leia wouldn't work, Vader instead turned to Chewie, forcing him to give up all of the Rebels' secrets. The entire Imperial fleet jumped the Rebellion, instantly crushing the Alliance to bits. When the Alliance was destroyed, Chewie and Leia would be executed.
__________________ "Once more, the Sith will rule the galaxy! And... we shall have... peace."