An idea I had for CT3 to keep CT1 and 2 relevant.
CT3 wouldn't drop unique gear. Instead, it would drop something similar to what we have right now in the 2.4 dungeons. Ancient helm, body, etc that you exchange along with gear from CT1/2 with of the same slot. For example, you win the body token. You can then use this to upgrade any of the CT1/2 body pieces for an augmented version of it that's i120.
Alternatively, you must exchange body pieces of the same role (caster, tank healer, etc.) from BOTH CT1/2 and get a unique looking i120 gear. The special token would have a weekly lockout. Gear from CT1/2 would not.