Firstly, I don't expect Vader to come on the armor body, that body is meant for fully armored figures like Stormies and Clones, Vader has so little armor the body would look like crap where there's no armor. That or he'll be some hybrid of the armor body and Prometheus or something.
Secondly, as far he should be ready and all that, here's my take. Their first "clone" was Obi-Wan. To me, that's a calculated move to gauge whether people are happy with the final result they achieved or not on a figure that is passable for most if it flops. If we see clones at SDCC, my bet is we wouldn't if Obi-Wan had been a flop with collectors. So that said, as much as Clones and Stormies are popular with folks, they're not Darth Vader. I think most people would agree that Vader is THE character to represent Star Wars, the most recognizable appearance and impacting character from the saga. As far as I see it, Sideshow's first Vader has A LOT of pressure on it. With themselves as the artists behind it, with LFL as the rights holder, and with collector's as their market, there is a great deal of demand for Vader to be the absolute best he can. The anticipation, as demonstrated by the frustrated posts around here, for him to finally be done is so high, there is NO room for error with people, if they slip up in a way that flusters more than 15% of the collecting community, it'll be the ^^^^ storm of all time. I won't be shocked if he's not at SDCC, he will come when they feel most confident in their figure and LFL has given a full blessing on it.
