Rivalries are ideally reciprocal. The other team gets as amped up to play and beat us as we get to play and beat them.
In that context Pitt might be the closest thing we have to a rival in the ACC. It doesn't matter that they've had a couple of down years, rivalries are not formed from a two or three year run. Pitt is geographically close, they are in our current conference and we play them twice per year, we have a reasonably long history (same conference since 1982) and regular matchups prior to that (116 historical meetings) and we've each had periods of relative dominance over the other. To me, like it or not, they are our best current prospect for a "traditional" rival.
If we can continue to play either Georgetown or UConn on a regular (at least every other year) basis, I think either or both would also maintain status as a rival. Villanova would be a good third option. I couldn't care less if we ever play Rutgers, Seton Hall, Providence or St. Johns; they are more nostalgic than rival.
Conference opponents that are the best candidates to become rivals, aside from Pitt, would be BC (if BC upgrades some) and possibly Notre Dame. Mostly because they need rivals, we are and have been competitive with them and we have history.
Until we get the program back to a place where other teams are worried about having to play us, I don't see any traditional ACC memeber truly being a rival. We may get amped up for a game against Duke (15 all time meetings), UNC (16 all time meetings) or UVA (13 all time meetings); but I think we are a novelty to them and any sense of "rivalry" is a creation of the ESPN marketing machine. If we get back to a position where we are occasionally favored against those guys, maybe we'll form a rivalry, until then it's pretty one sided.
As fans we should embrace Pitt, Georgetown, UConn, Nova, BC and Notre Dame as rivals and stop worrying about whether playing them will somehow help them more than us or be beneath us.