Even though they cannot appear with a full squad, there is no reason for them not to try as hard as they can to win the match. I can't say that they will fail to defend their title this season, but I also can't say that they will succeed in defending their title, because after all, both opportunities are still very open to them. There are still 2 clubs that are competing very closely with them and it is not yet certain whether they will succeed or fail in this very tight competition.
In fact, Manchester City also has an even squad depth, although it won't be like their main players, but at least they don't have any significant differences. Now it's just a matter of how the coach prepares it all, and he must be able to ensure that the players he trusts to play can give the best performance they have. Before the competition ends, there are still opportunities during that time. This applies not only to Manchester City, but also to Liverpool and Arsenal. Especially when the distance between them is very close, it is possible to change only a difference of 1 point.
Guardiola has very good depth, benches, but this also applies to Arsenal and Liverpool, so the conditions are equal for everyone. The most important thing is that all the main players are in the game, injuries can affect it, and players from the bench cannot always fully replace them.
Liverpool could top the table again in the next round if Arsenal lose points. I don’t believe that City will lose at home, so I think that Arsenal will not be able to retain the lead for very long. They are lucky that there is a short break in the championship now, and they can enjoy being at the top.
Yes, what you say might happen, that Arsenal will not be able to maintain their position for a long time, because the position they currently occupy is the result of taking advantage of the results of the match between Manchester City and Liverpool when they met. However, Arsenal also still has the opportunity to maintain their position in the current standings, although their chances are not greater because the opponent they face is Manchester City.
If Manchester City can win, then they will return to 3rd place in the standings, and that will look at the results of Liverpool's match because if Liverpool wins then Liverpool will return to the top, followed by Manchester City. However, if Liverpool lose, then Arsenal will be in 2nd place because they are still superior in terms of goal productivity. However, I don't see Liverpool losing this match, because the opponent they will face is not a strong club, so it is very likely that they will win in the coming week.