I don't think that DPC is milking. Milking is what creators such as ICSTOR have been doing: raking in support without working on the game, and doing the bare minimum to keep the support going. DPC is not doing that. He is taking his sweet time, sure, but the update will also contain 5,000 new renders, and likely a total animation length that is longer than his previous updates. Therefore, I cannot accuse him of milking, because he is producing more with the extra time he's spending.
However, I would be lying if I said that I didn't think creators take note of the fact that they can spend an increasing amount of time on updates without losing any support over it. When Episode 9 finally rolls around, it will have taken 2-3 months more to produce than Episodes 7 and 8, yet DPC's patron count has been hovering around the same level. As DPC's income is directly tied to how long he develops a game, it makes sense for him to extend that time as long as possible. I mean, why would you release a game in three years, when you can just as well take five years and generate more income?
As mentioned, though, I don't think he's milking, because it's not like he sits around on his ass waiting to release an update that is already finished.