My main theory is that Kratos is gonna die in the next game or two by Thor (Frea will likely choose that moment to get revenge, maybe alter Atreus' memory) then Odin adopts Atreus into their pantheon because of his level of power (his mixed bloodline) to use. It fits into the lore of Loki. Atreus recovers his memory somehow when he's an adult and seeks revenge against Thor and odin. Since Atreus is not his father, he won't wipe almost everything. More than likely he allies with Tyr.