Since there's a teaser trailer for it, that would be an enormous failure to fire Chekhov's Gun. That baby's gonna have some significance - you can count on it.
I think as a shot in a teaser, it may just be making it clear that Steve Rogers built a life for himself. Quite possibly in a timeline that Steve is forced to permanently leave for the greater good.
However, if you are correct, note that "significant" and "actually played as a meaningful, realized character" are not the same thing. The kid can be a McGuffin, effectively an object that moves the plot.
In the comics, Steve doesn't have any kids that have turned into permanent characters - the kids he has had have all been in alternate timelines and "What Ifs" that haven't then entered the main comics continuity.


