Avengers: Endgame
This is a potential title that’s only popped up since Infinity War arrived in cinemas. That’s because it’s not the name of a comic book but references a line said in the movie itself. After Thanos has got hold of the Time Stone and heads off to Earth in search of the last one he needs, the Mind Stone, Doctor Strange makes clear how dire the situation is. “We’re in the endgame now,” he tells Tony Stark.
It’s widely suspected by fans that Strange will prove to be very important in Avengers 4, so naming the movie after something he said in the previous installment could subtly prepare the audience for a twist to come with his character. Though he’s currently dead, there has to be a bigger reason why he caved in so easily and gave Thanos the Time Stone. Like he tells Iron Man, “it was the only way.” Presumably, this was a nod to the fact that he was making sure this timeline was the only one out of 14 million – which he’d foreseen earlier – that ends with the Avengers coming out on top.
On a more general note, Endgame would be a fitting title as Avengers 4 does indeed mark the endgame for the first decade of the MCU. As we’ve been told a lot, the franchise will practically begin anew with Phase Four, so this would be a suitably dramatic way of signposting this as the end of an era. It’s also another “scary” title, fitting in with what the Russos said.