Atlanta remains the sole credible threat to unseating the Cavs as default East champions. Even with all that player movement, I don't see any other East teams competing in the ECF.
edit: to your final point, though, yes - it could make things slightly harder on Cleveland trying to guarantee HCA in the Finals over a Western opponent, but considering the firepower of my picks for the West Top 4: Golden State, LA, SA, and Houston, they'd probably have a hard time getting there regardless.