Persona Q2 has been in the works for quite some time, and was planned for 3DS-only from the start. In an interview with Famitsu (translated by NintendoEverything), producer Daisuke Kanada explains how the sequel got off the ground.
When the previous game was released, I was able to garner a great deal of feedback from it, thankfully. I was really happy that people enjoyed the crossover between Persona 3 and Persona 4, the chibi-style characters, and the Persona-esque mechanics and story. PQ2’s development began relatively soon after Persona 5’s development had ended; since characters from both Persona 3 and 4 appeared in the last Persona Q game, I had basically decided from the very beginning that I wanted the full Persona 5 cast to appear in the next game. On the other hand, though, a lot of players said the “horror-like” atmosphere came from the amount of difficulty spikes – and I will admit, the dungeons might have had level thresholds that were too high. This time around, though, I can assure you that we spent a great deal of time making sure that you can play through to the end of the game easily and comfortably.