I think alot of this depends on what the Celtics FO thinks of Tatums recovery. Pre injury, Tatum was taking a playmaking step that was fantastic to watch. I know the Knicks bogged us down, but Tatum was picking apart defenses before that like we hadn't seen in his career.
If they think post injury, he can be the primary creator with Giannis as the recipient on high volume...you have to do the trade.
If they think Tatum can't be that, but can be just the best 6'10 connecting player with great shooting, great defense, etc (aka like 2nd half of paul George's career) then you might need to keep Jaylen.