I think LeBron is ready to erupt, I think he's being used wrong and is actually already one of the top 5 players in the league. He's only going to get better too, so whether it's just an improved DC or LeBron just getting to the point where he's amazing in all TCs, he's due for more of a jump in the next couple of seasons.
The obvious answer for regression is Shaq. He's on the first year of a big five year deal, he's 34 and due to start regressing. That contract is going to get ugly towards the end of it. I think he's always going to be serviceable until he retires, but he won't be worth the max money at the end of the deal.