For starters Lee would relieve Longstreet of command. The question is who Lee picks to order the attack and who he picks to replace Longstreet in charge of the first Corps.
Two of the three divisions selected to lead the attack are from AP Hill's 3rd Corps, but Hill is incapacitated and Pettigrew and Trimble have just recently taken over their divisions, replacing a wounded and a dead officer.
Meanwhile, the division commanders for the 1st Corps are Law (temprarily replacing the wounded Hood), McLaws (previously passed over for Corps command by Lee in spite of Longstreet's recommnedation), and the largely untested Pickett.
So my best guess is Pickett becomes commander of the 1st Corps, with Garnett replacing him as division commander, which may just save him life.
Pickett's charge would still be a disaster as it was on OTL. And Pickett's Corps probably wouldn't be sent west to reinforce Bragg. Even if it was, I doubt Pickett would manage the breakthrough that Longstreet did at Chicamauga. And with Pickett instead of Longstreet, the Battle of the Wilderness could easily be a crushing defeat for the Confederates.