I can't find any information about when Saka will be able to return to the game, but it looks like he has a serious injury, at least Arteta was upset when he said it. But it looks like Arsenal are playing well without him, Saka has been out since the end of December and Arsenal have played a lot of important games during this time, it looks like they have learned to play without him, and of course his return will strengthen Arsenal's attack, because he created a lot of scoring chances.
Overall, losing Saka due to injury does not have much impact because we can see that Arsenal is still quite consistent even though his loss gives a slight setback in terms of attacks built by Arsenal players but in terms of goal scoring quality there is no significant impact and maybe as you said because Arsenal is starting to get the right formation even though Saka cannot play.
His presence is considered quite important because it can increase Arsenal's attack to be more dangerous, but I see Arteta starting to find a formation to cover the gap. Arsenal will face several big matches in the future and his presence might be able to increase the attack power to be better.