Feige’s confirmation that Loki aligns with Thanos in Avengers: Infinity War was passed along by Brazilian entertainment news outlet Omelete, via their Twitter account.
Additionally, it’s also possible that when Loki aligns with Thanos, he’s not actually betraying his brother and his fellow displaced citizens of Asgard.
During an appearance at Brazil’s Comic Con Experience event, Marvel Studios boss Kevin Feige confirmed that Loki aligns with Thanos in Avengers: Infinity war. This isn’t entirely surprising, as the hotly anticipated Infinity War trailer confirmed that Loki had in fact swiped the Tesseract before Surtur laid waste to both Asgard and Hela at the end of Thor: Ragnarok.
Unfortunately, they say a tiger never changes his stripes, and the same principle might hold true for Loki.