I think Arsenal has a better chance of beating Manchester City in their Premier League match on Sunday at Etihad Stadium. Three Manchester City players were injured while on international duty for England, and there are doubts about being ready for the Arsenal match. This will be an advantage for Arsenal. Arsenal will dominate most of that match because John Stones and Kyle Walker are among the injured Manchester City players.
If the players you mentioned are unavailable against Arsenal, I do not think that Manchester City will win the game since Kyle Walker is the best defender in Manchester City. If Manchester City's injured players are unable to play against Arsenal, Arsenal will have a major advantage to win and dominate the most of the game, despite that Manchester City will host the game. We don't know if De Bruyne will be fit for their next game against Arsenal after getting injured against Liverpool. I thought only De Bruyne would be absent, but now John Stone and Kyle Walker will be unavailable. It will definitely have an impact on their game against Arsenal.
As long as there are still replacement players for the line usually occupied by John Stones and Kyle Walker, I don't think Manchester City will immediately become weak because of this. Because the Manchester City coach himself will also think about this more seriously because remembering that the match is at Manchester City's home ground, the Manchester City coach will choose players who are more suitable to fill that line so that the match can be exciting and it won't be easy for Arsenal to win there.
You're right. Pep Guardiola may choose another player to replace Kyle Walker and other players in their defense line against Arsenal, but they will not be as powerful in defense. Kyle Walker sustained an injury after playing 20 minutes in their international friendly against Brazil. We know that Manchester City may not be as weak as we assume, but they will not give Arsenal as much trouble as they will when the injured players return to play.