I don't see any serious contenders to unseat Cleveland as the best in the East. Their fourth consecutive conference title seems extremely likely. Boston will be improved offensively with the additions of rookie Tatum and All star Gordon Hayward but will take a step back defensively with the subtractions of Avery Bradley and Jae Crowder. The Irving/Thomas swap won't net a great difference. Thomas had an unbelievable season in which he was fifth in the Mvp voting, Irving has never had a season like that and it will be very hard to replicate.

Washington can score but just can't stop anyone on the other end so there's only so far they can go.
Toronto is a good solid team and if everything goes their way they can be the second best team in the conference but are not a serious threat to Cleveland. Milwaukee is on the come but they still need another great player to accompany Giannis before they can be taken as a serious threat.

After that I would group Charlotte, Miami, Detroit and Philadelphia together fighting for playoff spots with one team bring left out.

And finally Indiana, New York, Orlando, Chicago, Brooklyn and Atlanta are lock lottery teams in my opinion.