I can assume that Pogba's location will depend on whether Real Madrid can conclude a contract with Mbappe and Haaland at the same time. If yes, then this opens the door to PSG, if not, then Pogba will be a good replacement for Modric, who, in any case, will not be able to play in Real for more than one or two seasons.
I read few days ago that Haaland is not interested in joining Real Madrid if Mbappe is there since he won't be able to shine so he prefer in that case Barcelona so they will reproduce the CR7 - Messi phenomenon.
The question is will Barcelona be able to afford him with the salary demands that he may come along with?
I also don't think Real Madrid will sign both players. It probably has to be one of them, for now, Unless if Benzema decided to leave soon.
For Pogba he will be a free agent and every team will accept him in if they will be able to afford his salary. I think he will play for Real Madrid or PSG next season. For Modric, he is still a key player in Real Madrid and Ancelotti will keep him for a while unless he won't be able to add anything to the club.
It's Zidane who mostly wanted Pogba. I don't see Pogba going to Real Madrid. Maybe if Zidane signed for PSG. Chances of him going there would be very high.