If he lets his contract run down to the final year, which he should, he’ll be in line for a massive pay day. Either from Arsenal, who I’m sure will pony up as best they can to keep him, or - if he keeps his current trajectory - he’ll get a big club/big pay day move to someone like City, PSG or Real. He’s a top player and I think he’ll go to a title challenging side, as he’s just going to keep getting better. City would be perfect for him unfortunately.
He may have an affinity or loyalty to Arsenal that keeps him there, but if he prioritises personal ambition I think he’ll probably end up at City or one of the big continental clubs.