I think/hope Sony's reveal will be more like Vita's in terms of the relative absence of CG stuff and the spotlight on live stage demos and real game footage.
If PS4's launch was still 18 months out, then I'd expect a lot more CG etc ala the PS3 reveal (which was well ahead of release). But if they're really announcing so close to launch (within 9 months?) you should be seeing a lot of 'real' stuff. I'm sure there'll be some CG but the ratio should be way lower than PS3's reveal.
Given that Western developers actually care about consoles, they should be able to pad out any early reveal with a fair amount of cross gen games that are targeted for Fall 2013/Spring 2014 as opposed to just next-gen only games, since those would very likely be ready for reveal by now.