yeah, and I can't really blame them for including his image in the marketing. He's such a universal figure at this point.
But the general public seems to be waiting for Vader to appear in these movies. When talking to my friends about the PT everyone always wants to know "when will Darth Vader finally be in the movies?". Its what everyone wants, and they've played up to it so far with the first teaser poster for TPM and the teaser trailer for AOTC (and there's probably more but I can't really remember). They'll play it up even more this time, with Vader probably appearing in the trailer and/or on the poster. At this point its going to be tough to get the point across that its the birth of Vader they're about to see and not the life of Vader.
Everyone will see Vader and immediately think "OT!!!" (well, not OT because they aren't fanbitches like us, but you know what I mean

).