The GTX 960 was, at best, comparable to the GTX 770. The GTX 970 came close to the 780Ti in some benchmarks, beat it in some, and was trounced by it in others. As such, I don't see where you're getting your "trend" of two-tier intergenerational jumps from. Pascal was an aberration here, due to the process jump allowing both higher clocks and more cores on cheaper chips at the same time. Although Volta is 12nm, I sincerely doubt we'll see anything comparable. Single-tier performance improvements (or dramatically larger = more expensive dice) seems far more likely. That V100 is ludicrously large isn't really indicative of anything on the consumer side.
As for TDPs, the 780Ti and 780 were both 250W cards. The 770 was a 230W card and the 760 a 170W card. The 980 was a 165W card, with the 970 at 145W, the 960 at 120W and the 980Ti at 250W. The 1080 is a 180W card, the 1070 is 150W, and the 1060 at 120W. Again, the 1080Ti is 250W. In other words: they're all over the place except for a hard upper limit at 250W. Other than more powerful cards in the same generation needing more power, you really can't say much based on this at all.