IMO, Devin Booker isn't the problem. He might even take less than a super max deal when the time comes around.
Listening to Gambo, I understand Devin Booker is not going to play through another rebuild and the Suns are indeed keeping him. I suppose this could change, if the Suns have to completely rebuild, but this seems to be what it looks like at the moment. Needless to say, the Suns need to trade Durant and get meaningful talent and draft picks in return. Other players such as O'Neale and Allen could be traded as well to get below the second tax apron.
Getting rid of Beal's contract is a wild card. In the right trade, if the Suns could acquire multiple first round picks such as in a Durant trade, I could see the Suns having to attach assets to trade Beal.
Having three huge contracts on the payroll is simply too much and the Suns are finally realizing this.