Jeff Kaplan posted a reply in another topic indicating they are removing the current portrait system.
currently our plan is to change this system for ow2. we’ll find a way to recognize your accomplishments for those who care but the current plan is for those borders to go away and be replaced with a different system.
Also, I remember WyomingMyst had posted a screenshot before of his playthrough of the Overwatch 2 beta he got to play at last year’s Blizzcon, and the border frame surrounding his hero’s portrait wasn’t even there. I don’t have the link though.
Edit: whoops- FuityXNinja beat me to Jeff’s quote.