People who think McTominay will be dropped are setting themselves for a big disappointment.
Fred will be a regular starter, as he should be, and unless we play some absolute bollards, so will McTominay. I actually expect Scott to have more minutes than last season (assuming we don't add a midfielder, what seems the most likely scenario right now).
There is no way Eriksen will be a regular starter in midfield two, he never played that role, and that's not why we got him. Not without a proper DM behind, which we don't have.
Eriksen is not Pogba replacement. He's here to give the team another option in no10 position, as he's a very different player to Bruno.
The only chance to drop McTominay is if van de Beek improves and takes this second midfield place. That is quite possible. He for sure will have plenty chances this season.