While all of this is true, keep in mind this is December. A lot can and will change. The Browns will hopefully have improved their tackles and will likely have a new offense next season. Chubb has proven to be much more of an asset in the passing game than anyone wanted to give him credit for and has shown he has a game breaking top gear. Mayfield is a pretty good QB for a running back to be paired to. He's not going to throw for 40 TDs next year. The best RB TD seasons were paired with efficient, but not elite QBs: Shaun Alexander and Matt Hasselbeck, LT and a young Brees, David Johnson and an old Carson Palmer, Priest Holmes and Trent Green. Chubb has 10 TDs on 201 touches. If things improve next year it's not hard to imagine him scoring 20 TDs on 300+ touches.In PPR, Chubb is #10 in ppg in weeks 7-16, at least for now (Lindsay could pass him tonight).
In weeks 7-16, he has 167/799/6 rushing (4.8 ypc) and 18/153/2 receiving (8.5 ypr) in 9 games. Scale that to 16 games and it is 297/1420/11 rushing and 32/272/3 receiving = 1692 total yards, 14 total TDs, and 32 receptions.
The rushing production is very strong, but his receiving production is not on par with the RBs most rankings have ahead of him (Gurley, Barkley, Elliott, Kamara, McCaffrey, Gordon).
No way he belongs in a top 3 ranking of RBs for next season.
That being said, there's no way to confidently project Chubb as a top 3 in PPR. If Kamara and CMC continue their reception pace, it'll be hard to keep up. However, a couple things to keep in mind:
https://twitter.com/PFF/status/1077395779868778496
https://twitter.com/PFF_Sam/status/1075068026876256256
In auctions next year, I suspect Chubb will be going for at least 20% less than the guys listed in this thread. I think I'll take that discount and see how things shake out. I think he's the most likely guy to break into the top 5 who will be routinely left out of consensus top 5 rankings.