If it's (awful word inc.) canon, I expect P3 MC to show up. Elizabeth was out trying to bring him back (or rescue his soul or whatever) during P4. There's also something about placeholder data on the site that suggests it as well.
Probably covered already, but who did the soundtrack, anyway? They should've just sent Ishiwatari and Meguro to the studio with a bunch of rum or something. Don't come back 'til you're done.
To be fair, the worst case scenario here is probably... worse.
Even June 3rd is speculation based on a) the store coming back up on time, and b) the store not breaking again when it returns.
I'd accept that date as a minimum, quite honestly.
There's also a possibility that pretty much any game will need to be patched in order to work online with PSN's new infrastructure (depending on severity of the overhaul), and that would likely have to be addressed by the developers and not Sony.