4th option will be either Jaylen or Hayward. I wouldn't be shocked if either of them outscored Tatum (especially Hayward) but I can't see both of them doing it. Kemba will probably be the #1 scorer but it's also plausible Tatum catches him.
People underestimate Hayward scoring...he's capable of some big nights. Even last season he had 3 games of 30+ points, which is more than anyone else on the team other than Kyrie. He also had 26 30+ scoring games in Utah in just his last 3 years with them. The problem last season is he also had 30+ games where he scored single digits. He's capable of scoring, but I'm guessing what happens this season is he averages somewhere in the 15-17ppg with the occasional big night, and continues to be the main facilitator of the offense and helps others score, particularly with the departure of Al. Tatum on the other hand will probably carry the bulk of the scoring along with Kemba. I haven't yet seen Tatum really grab hold of a game and dominate it. He's only scored over 30 once in his career. I'm sure he will get his opportunities this season, along with JT. Kanter will be good for 10-12 ppg on average, mainly on putbacks.
I made a table of our team's top six scoring spread last season. All data from Basketball Reference.
What I really, REALLY hope for this season is that they all learn from last season - being unselfish leads to better shots for everyone. Too much iso and trying to "get my shots" leads to disaster more often than not if it's done at the wrong time. Having people singlemindedly focused on "I'm going to be an All Star, I'm going to average 20+" is good as long as it doesn't lead to selfishness and failure to put the team first. If JT averages 30, makes the All Star team but our team doesn't make it out of the first round of the playoffs then I will be disappointed.