I think p5r means persona 5 rumble. It makes a lot of sense because Atlus tends to codename their games. I got this from Johnneawesomes video though but it seems to be very likely.
I presume it's gonna be something along the lines of Persona 4 Golden.
Perhaps Persona 5 Red or Persona 5 Ruby.
I personally thought Persona 5 Crimson would've been a better name but Ruby is alright.
persona 3 sapphire when
Persona 5 Reloaded sounds fucking stupid.
Even Persona 5 Red would sound less dumb than "Reloaded", because "Reloaded" sounds like something you'd put at the end of a remaster of an action film that nobody cared about.