Again, it depends on what is offered for Phillips. You can't say that the best move is to trade him now without knowing what offers are on the table for him.
IF the front office can get fair value for him, and IF they will replace him with someone other than Albies for the remainder of the year, trading Phillips is the right move.
Assuming you can get more than nothing, then the right move is to trade him. He's gone after this year either way, and we have not yet started our window. Yes, we are .500, but it's still not likely we are going to make the playoffs. Get what you can now, especially since his value is peaking.
Again, Albies is going to come up when they decide they want him up. If that is now, they will trade BP just to make room. If that is not now, they won't bring him up even with BP gone.