Jeff Kaplan Overwatchś Game director confirmed on the battle.net forums that they are not particularly thrilled about having a split screen in the game. Split screens are useful for couch gaming. Console players who are together can play together and it was fun a few years back.
But split screen gaming definitely has lost interest of the players and the number of people interested in the feature is definitely much less than before.
We don’t have any plans for this feature right now. I wouldn’t go so far as to say “never”, but this isn’t one of our current priorities.
Check out Jeff Kaplanś reply on the battlenet forums here.