As I've pointed out before, if you're going to play through to get to the Shawna content, then waiting just means there will be that much more to make it through then.
If Shawna content is all you're here for, then you'd be better off moving on to another game. As the dev has said, Shawna (and Aiko) were basically just there so there'd be some sexual content while the MC was becoming acquainted with the women of Gilford. While this is not (to date at least) a particularly plot-heavy story, the MC has been given time to actually get to know the other characters before whipping it out, for the most part.
While some sort of a return for both characters has been promised, one is inclined to assume that: a) the will happen late in the game, and b) they won't necessarily be the focus of attention even then (I'm envisioning some sort of orgy-type event with everyone you didn't avoid during the game, but that's just a wild-ass guess).
TL; DR: While one more appearance by Shawna has been promised, it's hardly likely to be worth skipping the entire rest of the VN to get to it (or even skimming through all the images).
but their relationship is one of the few ones that doesn't progress at a super fast pace.
