Unless he is being rested, I think Miller will be in the regular rotation, and if for whatever reason he doesn't play in a given game, very probably either James Jones or Joe Harris (unless he is in Canton) will, or Ray Allen, of course.
Haywood will play against certain teams in certain matchups.
Amundson will play garbage minutes or occasionally will fill in for injured players or if the Cavs have bad foul trouble or during difficult stretches in the schedule or when the team is flat and needs some energy. He'll probably get in more games than people would guess.
Caveat: All of the above is just my opinion, of course.
Vardon's article states LeBron has averaged 39.5 MPG across his career, but the more operative stat is the number of minutes he has played per game in recent years, which is as he points out more like 38. He averaged 37.7 last year even with Wade sitting out 33% of the games.
I think shooting for no more than 37 MPG should be a goal. Some on RCF have thrown out numbers as low as 30-32 MPG, but that's just not realistic.