Avengers 4: 10 Rumours We Know Are Bull
5. There's Another New Stone
The Rumour
The question of how Thanos can be defeated when he's in possession of the most powerful artefact in the universe is a pretty pressing one and it's inspired lots of theorising and rumour-mongering. One such rumour suggests that the only way the Avengers can possibly hope to defeat him - rather than going into the past and messing up the timeline entirely for themselves- is to find something even more powerful that could undo his evil acts.
Specifically, that would be a seventh Infinity Stone - like the Ego Stone from the comics - which would be more powerful than all of the others combined. A sort of "One Ring to rule them all" style deal. And that's why the Avengers are journeying through time and dimensions in Avengers 4: to find the lost stone.
The Debunking
It's unlikely that the Russos would make a two-part film in which the second part made the first one entirely redundant with such little effort. Revealing that the most powerful weapon in the universe effectively has a kill-switch out of nowhere would not be a good thing for fans and you'd hope that the directors would know this much.
All that would do, also, is present another possible villain with something to aim for that was even more powerful