#1 He will be much happier under Mikel Arteta
Of course, it was Unai Emery that made the big-money move happen back in the summer but it just seems like Pepe's morale is greater under Arteta. This can be said for the squad as a whole too, not just Pepe.
Arteta has been known to improve many players at Arsenal since his arrival, including Granit Xhaka and Lucas Torreira. Consequently, if Arteta is the option for Arsenal's long-term future, then Pepe and his teammates are in safe hands and they can flourish into better players .
Arteta will continue to give Pepe all the freedom in the world for as long as they have top quality and high-scoring forwards. That said, the Gunners aren't exactly in short supply - with Lacazette in his prime years and Martinelli not even hitting 20.
Pepe is still in the first year of his contract so the club still haa plenty of time to prove to him they are the right club for his future. However, keeping ahold of Arteta might just be the best way about that.