Cali, I've missed you. And yes, in the case of this group (the Big Four), talent seems to override age...at least for awhile. The Grigor-Milos-Kei group has essentially been bypassed in terms of the passing of the baton of dominance; it will likely skip over those guys almost completely to Zverev and his group, when they are ready to claim it.
That said, things will likely equalize over the next year or two as the old guys inevitably decline, the middle group solidifies as the new second tier, and the young guys get better and better. As I've said at TF, we're likely entering a "Wild West" period in which anything goes. Maybe 2017 will be one more year of Big Four dominance, but I think they are--as a group--more vulnerable now than they were a year or two ago. At the least the gap will continue to narrow.
I've also made the point that while 30-year old Rafa (or 29-year old Novak) can still beat a 25-year old Grigor (or 19-year old Zverev), what will their matches look like in a couple years, when Rafa is 32-going-on-33, and Grigor is 27-28? (or Zverev is 21-22?). In other words, the "lost generation" might still get their chances, as the Big Four inevitably decline and the "GenNext" haven't quite reached their prime.