With the reveal at Disney's D3 Expo at Anaheim of the Children of Thanos, aiding the Mad Titan in his assault on the heroes of the Marvel Cinematic Universe in Avengers: Infinity War, there's an interesting point to note.
As I mentioned in the reveal article, the characters revealed as the Children of Thanos are in fact the Black Order, or Cull Obsidian, introduced in the comics in the Jonathan Hickman written event Infinity. In it, the Black Order were lieutenants of Thanos, and not his children. In fact, it was revealed that Thanos has a propensity to kill his biological children, and the hunt for one such child, a son Thanos secretly had with an Inhuman named Thane, was the crux of the event.
So if the Black Order are now the Children of Thanos, and assuming they are his own children unlike in the comics, could this mean that Thane isn't far behind an appearance in the MCU?
Moreover, could his role be vital to the as yet unknown titled Avengers 4?
The title of Avengers 4 is apparently a secret because, according to Kevin Feige, it would be spoilers to Avengers: Infinity War. Some had theorised that Zoe Saldana had accidentally revealed the title in an interview, when she intimated it may be Infinity Gauntlet. But this seems unlikely. We all know the Infinity Gauntlet is in play, so it would hardly be spoilers for the fourth Avengers film to be called it.
What if, instead, the plot of the fourth film revolves around the quest to find Thane? Perhaps the Avengers and assorted heroes of the MCU find out there is another Child of Thanos, one who rebelled and perhaps has the power to stop his father. Maybe, Avengers 4 will be about the heroes trying to find this child in the hopes he can help them defeat a triumphant Thanos, even with the power of the Infinity Gauntlet.
Maybe he'll even defeat his father the same way as in the comics, trapping him in an amber construct in a form of 'living death'…and maybe it will see the Collector take the trapped Thanos as a new item in his bizarre collection, keeping the universe safe from the Mad Titan (and suitable revenge after what appears to be Thanos' assault and destruction of the Collectors collection in the teaser trailer descriptions revealed from D23.
Maybe the title for Avengers 4 is actually something like Avengers: The Son of Thanos?