The Gunners don’t face Manchester United in a league fixture until December 3rd, over four months from now.
United aren’t in the Champions League, and the FA Cup doesn’t kick off for Premier League teams until January, so there’s no prospect of an imminent meeting in either of those competitions.

Of course, it’s possible that Arsenal could draw United in the League Cup, with the third round taking place in mid-September.
That seems like the only Arsenal game Yoro could realistically miss, and Hojlund should be back by then.