If we are trading for AD say before the draft, if the deal is Smart, Tatum, Williams and a package of picks. You make the trade. Tatum is not untouchable. If it's between Brown and Tatum, I would want to keep Tatum but if it means losing Tatum to secure Davis, you do it.
With Kyrie, Davis and Hayward, Tatum would be relegated to a third or fourth option anyway.
Kyrie
Brown
Hayward
Horford
Davis
is still a multiple title winning team, even if Tatum isn't here.