I believed Arteta is looking ahead to the end of this season before signing new players, however I don't think he knew the task of clinching the UCL spot will be very challenging if that spot is guaranteed quality players will sign for the club.
Yes, although currently the difference in points between teams in the top 5 is very thin, but Arsenal's next opponent is Wolves, which incidentally is also chasing points to reach the top 4 position. After all, this is the entrance ticket to UCL. If Arsenal are not able to overtake the 2 teams above just by beating Wolves later, I think it will be difficult for Arsenal to be able to rise again with the team's condition internally quite shaky because of Aubameyang's departure even though this is indeed the management's hope..
After Auba's departure, Arsenal might be in a bit of trouble I'm guessing. They don't have the squad depth needed to keep their players fresh. Although they are not playing anything other than EPL, still, having a good squad depth allows the coach to try out new combinations, and sometimes a lot of those work really well. But nonetheless, Arsenal might be having a tough time up ahead.