In Matrix: Reloaded the Architect said:
ARCHITECT: The function of the One is now to return to the source, allowing a temporary dissemination of the code you carry, reinserting the prime program. After which you will be required to select from the matrix 23 individuals, 16 female, 7 male, to rebuild Zion. Failure to comply with this process will result in a cataclysmic system crash killing everyone connected to the matrix, which coupled with the extermination of Zion will ultimately result in the extinction of the entire human race.
As we know, Neo failed to comply with this process, and thus should have had triggered the described consequences. However as we saw, there was no cataclysmic system crash killing everyone connected. Why?
Edit: please note the "this process" includes not only returning to the source "now", but also selecting individuals from Matrix. And yes, I fail to see how "failing to select individuals" can result in system crash, but this is what Architect said.
The argument that Neo eventually returned to the Source does not match with what the Architect said:
there are two doors. The door to your right leads to the source, and the salvation of Zion. The door to the left leads back to the matrix, to her, and to the end of your species.
In my interpretation this means the choice is NOW, and there is no option to "get back to Matrix" and then get to source and salvation of Zion. Unless Architect was lying.