A couple things to mention about leaks this time around and the people leaking them.
From what I've been told, and I trust my friends quite a bit, Vergeben has never been the person who originally has had his information. He is simply the person who decides to share it. Vergeben has also historically jumped onto stuff so that he can add to his own legitimacy, even if he hasn't actually heard of it.
Furthermore, Ken and Incineroar were known by a LOT of people. It's not like the only person who knew about it was Vergeben. It was considered common knowledge among people who knew, not to make it seem like you guys are "nobodies" or anything like that, but simply that people with connections knew about them being in, which then led to the whole Grinch debacle.
Basically, while I don't doubt Hitagi all that much based on their credibility with other rumors, they seem to be dumping a lot of vague information. It can be taken as either protecting their sources (makes sense if it's real) or purposely sounding vague so that there's better chances of being correct (makes sense if it's a lie). Either way, I'd wait before jumping on the "Steve, Granblue, Namco" train.
MysticDistance mentioned Lloyd, and that's something I'm really interested in (Tales of Symphonia is a fantastic game). That corroborates a Namco character, but anybody could corroborate that. It's the specifics that are more important.
I know some people are extremely skeptical of "insiders". But I would wait until more insiders say "Steve, Granblue, Namco hype train" before we take it as gospel. I say this because at this point, Verg could say, "Well, they seemed credible, but I was never told by my own sources that Steve was playable".
Believe what you want, but it's always good to question things to your own satisfaction!