I got to play with the proto at SHOT -- it's an awesome knife. Just from eyeballing it, the blade length was around 3.5". The stock of the titanium on the framelock was nice and thick, and the overall thickness of the knife was definitely greater than your average Spyderco (think something like the ZT 0550). Not sure what the steel was, but at least on the proto, the G-10 scale on the off side was tan.
As for whether they'll make it into production, in the display case with not-yet-released models, Spyderco had each knife labeled as either a "proto" or a "concept knife". "Proto" meant that the knife was going to make it to production and was a knife that Spyderco had produced (you guessed it) a proto of, while concept knives were just that -- knives that designers (often custom makers) had submitted for consideration but which may never see the light of day. As I recall, the Southard flipper was in the "proto" category, meaning it should make it to production. I certainly hope so, as it was a fantastic knife.