If I was going to speculate I could see Dez catching 6-7 passes for 75-89 yards but unless Dak is willing to give him a few chances down the field with jump balls it's hard to see Dez having a huge game. He has trouble running away from defenders so he needs to make a play down the field to pad his yards. Dak is being careful with the ball, he protects it he's not a gunslinger like Romo. Dez's best chance of having big, productive games would be with Romo because he's built chemistry with him over a period of years and Romo trusts him and takes a lot of chances down the field to him.
He trusted him enough to throw him a 50/50 jump ball in a playoff game with just over 4 minutes to play on a 4th and 2. Dak will throw one up to him we've seen it but he's going to throw to the open receivers most of the time. Dak knows if he's going to keep his job he has to protect the football and throw to the open receivers. He's still learning how to be an NFL QB so he's not going to be taking a lot of shots down the field just to please those who want to see him go deep more often. The system we have in place with him is working and we need to stick with the same formula.