Yeah I also think it's Boston or Milwaukee. Even if Miami gets Lillard, their bench becomes very thin, but also they already lost Oladipo/Strus/Vincent.
But then again, the C's have shown they can beat anyone... and choke to anyone.
They are the best team in the conference, it's up to them though if they want to actually play like it. They clearly didn't last Spring, going 6 and 7 games against much inferior Hawks and Sixers teams respectively, then going down 3-0 in the ECF to an 8 seed.
I do think some teams in the East will rise, but I'm not sure anyone is up there in the same tier as Boston and Milwaukee. Maybe Cleveland takes a step there? I don't expect much from PHI especially if they do trade away Harden and don't get Lillard.