MCU: 12 Things We Learned From 4Chan's Latest Marvel Movies "Leak"
4. Avengers 4 Plot Outline
The Rumour
Thanos will not be defeated at the end of Infinity War: instead the fourth Avengers film will feature the Avengers and their allies in their final battle against the Mad Titan.
Interestingly, there IS interest in bringing the Netflix heroes in for cameos.
Response
Given that Infinity War was initially billed as two films, it makes sense that Thanos' big show will cross over the end of one film. In narrative terms, because he doesn't yet have the Infinity Stones, it makes sense that the first film will concentrate on him getting hold of them and then a downer ending (possibly including some major deaths).
The Netflix thing is probably up in the air: we're frequently told that we're not going to see the Defenders on the big screen, only for a hint to appear that they actually will. Will it be a good idea? Of course it will, even with wildly different tones - who wouldn't want The Punisher to meet Rocket Raccoon? Or Groot, Hulk and Giant Man teaming up?