Discussing Timelines (spoilers)
The Ancient One tells Banner that he has to bring the Time-Stone back, so that her reality isn't doomed - not because the timeline gets branched - I think - but without the Time-Stone Dormammu would win and this (her) timeline branch would be doomed.
So - the MCU-Timeline will never be changed - but new branches of Timelines/Realities will be born every time somebody time travels and changes things - doesn't matter if the Infinity Stones are brought back or not.
Bringing them back only helps the branches/realities to be safe - may not have worked for all of them.
New Time-Line Branches:
- A Timeline where Loki escapes with an Infinity Stone - so Thanos may never get all 6 of them.
(or do they team up and everything gets worse)
- A Timeline where Thanos vanishes and doesn't come back (because he died in the future)
(The lucky Timeline for everybody ;)
- A Timeline where Cap lives next to everything that happens as an older version - crazy in love with Mrs Cap. (it is open if he changed anything here) (could be the same Time-Line as MAIN if he went undercover and Peggy lied on here dying bed to his younger self)
(wouldn't it have been genius if throughout all films the Superheroes received help from an unkown Mr X - which in the End would have been Older-Cap?
- A Timeline in which Tony meets his father in the 70s? Maybe they didn't change to much to create a new branch - except for being responsible for his own name.
- A Timeline where Thors Mothers met her Future-Son and Jane Foster looses the Infinity Stone for moments(?). Would have loved to see Cap meet Jane Foster. (could stay MAIN because the mother didn't want to know her future and Jane may have not noticed what happened - if she was unconscious)
But all of this cannot be one timeline - even if the stones are brought back.