Speculation about the teaser site Atlus opened last week seems to have settled on a port of Persona 4 for a portable system. Now for a more solid hint that something Persona 4 related is going to be announced soon.
This is the preview section from the back of the latest issue of Dengeki Maoh, a sister publication to Dengeki PlayStation which focuses on manga. Just ahead of the start of the Persona 4 anime and the release of volume 5 of the Persona 4 manga, the magazine is going to have lots of Persona 4 coverage in its next issue, including a special booklet containing interviews with the anime cast and a look back at the world of Persona 4. More notably, the magazine is hinting at a "major announcement."
Although Dengeki Maoh isn't a video game magazine, it wouldn't be too surprising for them to tease a video game announcement for something like Persona 4.
The next issue of Dengeki Maoh doesn't hit until September 27, so if the Persona announcement is video game related, expect to hear about it first elsewhere.
You can view the first volume of the Persona 4 manga here.