Personally, I was waiting for Barry and Iris to realize they needed to get going on trying to make Nora back when they thought Barry would die in the Crisis, so it would fit if Iris has a bun in the oven in the second half of Season 6.
One obvious guess about an event that will change a character’s life “basically forever” is Iris finding out that she’s pregnant.
That said, it would be kind of creepy if a pregnant Iris is one of the changes Oliver made for Earth Prime, so we’ll have to wait and see.