Seeing Aston Villa unable to maintain their position in the top four is very possible because their current position is quite helped by Tottenham experiencing a decline due to their players being injured, but I think Arsenal will stay in the top four and if they fail Arteta's position may be threatened, and Tottenham to be in the top four is very possible but West Ham doesn't seem like it, they can sometimes appear surprising but also disappointing afterwards.
Aston Villa only suddenly rise in this season and join top four and it will be very challenging for them to maintain good performances and defend their position in top four. Arsenal, Tottenham are two biggest competitors with Aston Villa with current table because Aston Villa have only 3 points more than Arsenal and Tottenham. They have same total matches like Tottenham but already played one match more than Arsenal. This means if Arsenal win their match, they will have same total points as Aston Villa.
Other clubs behind those three clubs will have many works to do to reach to these three clubs and I honestly don't consider they are big threats for Aston Villa.
The threat to Aston Villa will only come from Arsenal and Tottenham. And the closest is Arsenal. Because only Arsenal have not competed on Matchday 21. Meanwhile, Tottenham has done so and Tottenham can only get 1 point due to being held to a draw by Man United.
Actually, Aston Villa suddenly being in the top 4 competition was enough to surprise me this season. And I even thought that Aston Villa might continue to maintain its position in the top 4 until the end of the season. But after seeing Aston Villa being held to a draw by Everton, I started to doubt Aston Villa would continue to stay in the top 4 until the season ends. Because I think Tottenham and Arsenal will eventually fill that place.
But surprises are still possible in the remainder of this season. Because there are still many games left this season. around 17 matches are still open this season. And in 17 matches that is actually enough to make a big change in the standings.