It's been awhile since I've posted here (I blame you Tales of Graces f) but after seeing some screenshots I had to at least post a few theories.
1. The game engine seems to be based off the the Endless Frontier EXCEED engine which was incredibly detailed. Just looking at the screen shots we can see we have a combo meter as well as enemies being juggled in the air.
Above the bar in the lower right hand corner we can see five circles which occasionally have an arrow in them, which makes me think instead of just pressing A and stringing a set chain of combo's together we'll be using a directional based system ala the Tale's series or Smash Bros. Special attacks (Up, Down, Left, Right, or Center plus the attack button).
As for the gauge itself while it's labeled attack I can't help but think it's this game's version of the frontier gauge which let you preform your finisher in the previous games. I'm going to guess that it empties between encounters (unless you use something akin the spirit commands from SRW which may fill it fully or partially) and have to build the gauge up at the start of each turn or encounter with well chained strings of attacks or supports
2. Considering this is Banpresto we're talking about expect the villains from each of the series represented to show up in one form or another. I wholeheartedly expect Sigma to show his ever present smug grin at some point and for Wesker to appear. Also expect great care to be taken in somehow messing all these stories and series together, these are the people that "fixed" Gundam SeeD Destiny mind you.
3. There will not be a US Release. Sadly I'm gonna file this one under "Too Awesome to Exist" There's a couple of signs in the roster that show this was made purely for Japanese audiences with little chance of coming to US shores.The games Sakura & Ichiro (Sakura Wars) as well as Kurt & Riela (Valkyria Chronicles III) appear in have never been released in the US. If this had been Shinjiro, Gemini, Alicia, and Welkin I'd be more inclined to believe this was coming stateside Also there's the issue of Sanger Zonvolt. I believe that Atlus still holds the US licence for SRW and as such his inclusion means Atlus would either need to translate the game or give up those right. Frankly I'd prefer to see someone else take a crack at the franchise as Atlus doesn't seem interested in it these days or for Namco Bandai to actually do it themselves and give it the marketing push it deserves. Still though we did get Xenoblade and The Last Story despite the odds against them so maybe there is a chance we get this one.