We keep IT and 8th pick plus we still have Hayward. Thomas eventually gets healthy and is solid for the playoffs. Now we still have a great team without cutting IT's throat and team chemistry is even better. Going forward, we have a much more settled roster and a better chance to trade up for Mamba.
What we don't have is a flake for a starting point guard, who is self-centered and doesn't care who knows it. I say with a healthy Thomas + Hayward + Talented Post Defender we are better and are a contender for titles for the next decade. With Irving, we now have a bunch of uncertainty. I say Thomas would re-sign for a reasonable contract in the end because he absolutely loves being a Celtic.