Currently, Manchester City and Real Madrid are the two teams that are the favorites for people to win the UEFA Champions League next season if you are talking about teams that are qualified in terms of performances and squad in the team. Arsenal should focus on taking the Premier League from Manchester City because it is what fighting for. It will be a shame that at the end of all season, they still can't win the Premier League every time they get close. The only reason Manchester City will not put much interest in the EPL next season compared to how they will be looking at the UCL title is that they need more of the UCL cup and feel they can easily win the EPL.
In the last few seasons, Real Madrid and Man City always becomes the favorite candidates to win the UCL trophy. I think it is normal because Real Madrid has a great history in UCL, meanwhile Man City has a strong squad. Both teams also have best coaches and very experienced in UCL competitions. Man City and Real Madrid are also quite consistent to dominate the domestic league. It indicates that Man City and Real Madrid could keep their squad quality. This condition is quite different with other teams. Some top teams are experiencing bad financial condition, they can't keep the good shape of their squads. Other teams changes their coaches, so the team needs adaptation with the new strategies/tactics applied by the new coaches.
By the way, I think the team like Arsenal, Man City, Real Madrid, and other big teams, they won't focus on the domestic league only (local competitions). They must try hard to win the prestigious trophies like UCL and UEL. They will get big advantages if they win the trophies. So, I don't think they will focus on domestic leagues and ignore the chance to win the UCL/UEL trophy.