If you're talking about waiting for future unseen versions, then I think you have a point. But even then, I can see someone saying "what if I really love Civil War Cap more than AoU Cap?" Maybe there's some hassle that collector doesn't want to go through as far as possibly reselling a figure. Or maybe they're waiting for that one "perfect" Cap figure and are willing to not own a Cap until they find one. And I don't doubt that this mentality is much more common among collectors who only collect just one representation of a character.
Case in point, I still don't own an Iron Man figure simply because I'm waiting for the right one to come along. But based on what's coming out, I think this is the year that that changes. Or rather, I think this is the year where one comes along that I really want to buy, in spite of any unseen future releases that might make me want to resell the figure.