I would take: Kevin Durant, Kyrie and Anthony Davis.

But most likely NBA Players or European Stars will not play in the tournament:
"Baumann’s statement indicates that the event likely isn’t going to feature NBA superstars. I would expect FIBA to limit Olympic participants to players who have participated in the 3x3 World Tour or at least participated in FIBA-owned qualifying events."
(https://theringer.com/tokyo-olympics-2020-three-on-three-basketball-fiba-32ebdd92ca2dhttps://theringer.com/tokyo-olympics-2020-three-on-three-basketball-fiba-32ebdd92ca2d)