Assuming that Walker makes the team (and it certainly seems like he should), I don't see this as necessarily meaning that someone else will be traded. I would have preferred that the last roster spot go to a bigger wing, someone who can play the role of Tatum, but I think our roster balances out just fine as it would stand with Walker added. It bumps Hauser to a small forward wing role vs a guard wing role, but that doesn't really make any difference.
Combo: Holiday, White, Pritchard, Springer, Scheierman
Wings: Tatum, Brown, Hauser, Walker, Walsh
Bigs: Porzingis, Horford, Kornet, Tillman, Queta
or if you prefer:
Guard 1 Holiday Pritchard Springer
Guard 2 White Walker Scheierman
Forward 1 Brown Hauser Walsh
Forward 2 Tatum Horford Tillman
Center Porzingis Kornet Queta
Maybe Springer or Scheierman beat out Walker to make it into the top 10 rotation, I don't know, but it doesn't matter so much. Even our bottom 5 are pretty solid players for the most part. Springer, Tillman, and Queta have proven that they can fill in just fine when needed. Walsh and Scheierman are prospects who may surprise but that we don't expect to need much out of.