The biggest problem for me is the franchise being hostage of Davis and Kyrie. It's impossible to forget that both recently demanded trades from their teams and set back both franchises. Kyrie messed with the Cavs last playoff run and Davis created that whole deadline drama that we all know about.
Imagine if we sign both (Kyrie and AD) to multiple years. If something starts to go the wrong way for them, I'm not sure one or the other wouldn't demand a trade. We are not the Pelicans or the Cavs, we can't be held hostages by any player. The franchise is bigger than any player in this league.
So, my biggest fear with these guys is that apparently we would have to get rid of everything of value that we have to get them (Brown, Tatum, picks, etc), and then in two years we are without titles and both are demanding a trade to some other team.
I was watching parts of some games of the 2017-2018 playoffs again and Brown and Tatum played so good that is hard for me to think they can't become great players, specially in this day and age, with two-way wings dominating the league. I think that having a great wing duo is better suited for the actual NBA than a PG - Center combo (Kyrie and AD). It's not the 90's or the 00's anymore.