No, they'll fit, at least the vintage-spaced Gibson covers (Burstbucker, 57 Classic, etc., and all Gibson neck-spaced model pu cover's) will.
In other words, a neck-spaced cover or Burstbucker/57 cover will fit any of the Duncan vintage-spaced pickups, which I assume all non-trem-spaced Duncans are. Anyway, I know from direct experience that they'll fit Seths, A2Pros, Jazz's, etc.
The bridge-spaced Gibson covers (490T, 498T, 500T, etc.) MIGHT fit the Duncan trem-spaced pickups...but I've never tried so I don't know.