I think that's pretty bold. The Cavs might not be the 1 seed, but I think there's a good chance the Wizards pass the Celtics and there's also a chance that the Raptors do (less so without Lowry of course). The biggest advantage for the C's is their schedule, as you imply.
Just looking:
Celtics: 11 home games, 6 road games, only 1 b-t-b, though it's a tough one: CLE/@ATL. 6 total games against playoff teams, 2 against top 4 seeds
Wizards: 6 home games, 13 road games, 4 b-t-b (@SAC/@POR, CHI/@CHA, BKN/@CLE, @LAL/@LAC). 8 games against playoff teams, 4 against top 4 seed
Raptors: 9 home, 9 road, 3 b-t-b (@ATL/@MIA, OKC/@DET, @IND/@DET) 10 games against playoff teams, though only 1 against a top 4 seed (closing game of season against CLE)
So the C's have schedule advantage and maybe you say they are going to stay healthy finally (at least the starting 5) and play better than they have been. The Wizards have the worst schedule but have been playing the best ball over the past 30 games.
The relative positions of the C's and the Wizards is probably going to come down to their remaining HTH game, and how the Wizards do on their tough west coast trip (LAL, LAC on second night, then UTA and GS).