Thanos to cameo in Thor: Ragnarok

We have to mention this rumor, even if it’s a no-brainer: With the Tesseract in Odin's Vault, Thanos will have to come to Asgard. And what better time than when the Asgardians are battling for their own survival? In this way, Thanos could cameo in the end, when Asgard is still in ruins after the war with Hela and her legions.

At the same time, he could also give Hela a bit of extra power, which she would need to defeat Asgard. If it’s true that Hela is also Death in the MCU, the Mad Titan will have even more reason to be at her side (especially if he’s infatuated with her, as he is in the comics).

If the Soul Stone appears in this final Thor installment, he'll have even more reasons for being there. So this rumor is a no-brainer: of course Thanos will cameo during the final days of Asgard.