Arsenal is the only team that can compete with Manchester city as it stand, they have got the right player to give Manchester city a tough competition next season. last season they bottled the league because they got no good squad to rotate, every weekend it was just set of first eleven and they got some injuries issues too. But now they have a good bench to rotate and rest some players.
I don't think Arsenal is the only team that can compete with Manchester city in the premier league. They've got the right players alright, but Manchester City is far superior to Arsenal and this is just my opinion.
Admittedly, Arsenal suffered some setback due to injuries and lack of available players that could properly handle those roles. I still think Arsenal is a strong contender for the league cup along with Manchester United and perhaps Newcastle like you noted.
I would also like to see how Brighton would have prepared for the upcoming season. They had a somewhat good run last season and had given some big clubs hell on the pitch. I would like to see what preparations they've made for the next season.