For me hus biggest obstacle might be the French media.
If he is able to survive them, he might be able to somewhat challenge Pogacar already next year.
Pogacar has always been a huge underrated rider. I wouldn't be surprised if they say he can beat him even this year

. In his first year, despite winning Algarve and California, he was considered underrated. And he was underrated despite his Vuelta performance, winning 3 stages and that impressive performance on stage 20.
He arrived at the Tour de France without anyone taking him seriously. In the end, it was the best thing for him. With Seixas, the opposite will happen; he'll surely be on the cover of L'Équipe this year, and some will think he'll be sure in the podium, possibly beating Vingegaad and hoping for a mistake from Pogacar.
Luckily, he seems quite mature, because even Decathlon's DS is saying he'll be a future Tour de France winner. Even so, the French media are going to give him a hard time. For his sake, I hope he doesn't run into any problems and doesn't become another unfulfilled promise in France.