This is a potentially monumental revelation that Tony knew the risks of creating alternate timelines, possibly quite soon after he discovered a way to make time travel a reality in his log cabin. Even considering that Tony is regarded as one of the smartest individuals in the entire MCU, this reveal makes it clear that he thought of nearly every possibility as the team decided on a course of action to bring back their dead family and friends. This could have even been a reason for his trepidation when Scott Lang, Natasha Romanoff and Steve Rogers first brought this idea to his attention to begin with.
Via a new article from SyFy, an excerpt from the recently released “Wakanda Files” in-canon book discusses an encrypted text that Tony Stark sent to Bruce Banner sharing his findings on the time-space GPS they teamed up to create in Avengers: Endgame. Before the living Avengers pull their time travel plan completely together, Tony uses David Deutch’s model of Quantum Mechanics and sent this message to Bruce:
“…altering events of the past could never affect the continuous loop. Though, it could create tangential split-timelines. Let’s not worry about that for the time being, right? One reality at a time. For all our sanity.”
Tony may be gone now thanks to his sacrifice to defeat Thanos, but his theories on alternate realities are more of a possibility than ever before. WandaVision’s debut at the end of the year will almost certainly bring the first real teases for the MCU’s multiverse thanks to Wanda’s crazy new realities she creates, and the multiverse is also set to play at least some role in both Spider-Man 3 and Doctor Strange in the Multiverse of Madness.