This is the weird version that'll not have the portable content at all, right? That's such a shame, this could have easily been the definitive version if they made a Persona 3 Portable Reload.
Persona 3 portable was the portable re-release. However they released it with a lot of extra content. Content that people believe completed the package and made the game even better. As a result, many fans will experience a jarring feeling as the content they like will be very obviously gone. Hard to understand their decision. Maybe they planned to make it DLC. Sneaky buggers.
I'm almost willing to bet they'll release a Golden/Royal version a year or two after this version that has the portable content in it, if they do anything with the portable content at all. They wouldn't do something so consumer friendly as release it as dlc, they'll make you rebuy the entire game instead.
It was entire alternate playthrough with a female main character, new characters to build social links with, and a lot of new insights into the other characters of the game. The characters you fight with have different relationships with the female MC than the male MC. The PSP version had both playthroughs on one disc, though they had to make some adjustments like turning it into more of a visual novel style than 3d environments for the "town" segments of the game.
This is where I feel modders could get a very decent final say.
There will definitely be enough material to TTS the dialogues that don't exist in Relaod, and the text, sprites and models already exist spread between p3p, the rhythm game, etc.
I'd wager it's pretty doable to mod the content into the game once it's out.