I do not think Atalanta will be in the battle this season. They lost Gasperini to Roma, and they are looking like either they will lose Lookman, or they may just have Lookman who is upset that he wasn't let go, either case bad for them.
So Atalanta may not be as great as they used to be, because Gasperini was half of that team, and they lost him. I would instead put Roma to your list, who got Gasperini, because that feels like it's a lot better and he is going to make that Roma team great from the start. Roma did finish decently last year, but they started terrible, if they had a good start, they could have battled for the first place, it's quite obvious. We shouldn't really be considering this to be an ok situation, and we can't change that.
Lookman is no longer comfortable at Atalanta, but Atalanta's management continues to hold on to him. This will be bad for both sides, as it's highly likely Lookman won't play his heart out for Atalanta anymore, and his contribution will be different from before.
Gasperini's departure will change everything. He's a long-time manager at Atalanta and has made significant progress with a limited squad. The changes he makes now will certainly make a big difference. I'm sure Atalanta's performance will decline significantly compared to last season, making it unlikely they'll be able to compete at the top of the table.
By now I no longer believe that Lookman will go to Inter, if Atalanta wanted to sell him they would have already done so without much hesitation. A bit like it did with Retegui, form for Ademola Lookman things are a bit different! Atalanta would not want to sell him in Italy but only abroad so as not to reinforce direct competitors