I also won't be surprised if they end up not even winning any trophy too. Arsenal no doubt have played really well this season and also have being somehow consistent but one thing about this club is that they always flinch when the league is about to end. The reason why I feel the pressure might get to them is because of the two competition they are currently playing which is the champions league and premier league, it's an enormous amount of discipline and skills to manage the playing capability when performing to win or secure two trophies.
What you are saying is true because it has happened to Arsenal last season when they lost the opportunity they had on wining the premier League last season to Manchester City and they almost repeated the same thing again this season if not that they were able to regain there performance when the league is still on, however I don't think Arsenal playing on the two leagues will affect them because right now there focus is not really on the champions League because they know fully well that there are more quality clubs on the race for that trophy, so there interest now is on the premier League.