Business-wise it's unlikely that this is an enhanced re-release of SMTIV. If they wanted to do that, they would have already done that. To add to that, the main reason there is promotional stuff going on for SMTIV now is because the budget re-release of SMTIV is shipping in Japan this week on the 8th. So whatever this announce is, they're tagging along with that, hoping to get some attention and sell more copies to anyone who hasn't played it yet.
Could be SMTV, could be something new by the SMTIV team - like SMT SJ or whatever. Either way, I hope it's something cool with art style in that vein. I love Soejima's Persona 5 designs, but we need some Kaneko stuff or Kaneko inspired stuff to balance it out!