We'll still have a good team, but we won't have much chance of winning a champion. If we somehow manages to overcome the raptors or bucks and goes to the final, we'll face either Lebron + AD or GSW.
Also don't forget we'll need to pay Brown next year and Tatum the year after, if they keep on improving we'll need to pay max or close to max to keep them. In this league a borderline all-star and a superstar command the same max salary. So instead of paying superstar talent like AD and Kyrie, we might end up paying borderline all-star Tatum and Brown. It would only work out if two of Tatum, Brown, Hayward reaches all nba player level. Still possible but unlikely, given that none of them are killing it at the moment.
So having both Kyrie and AD is ideal, having one is Ok, having none is likely a set back.