Even if Lebron and Irving stay, the Celtics should be favored to make it to the Finals this year.
People magically forget that the 4-1 loss in the ECF featured a one-legged (one-hipped?) Isaiah Thomas for just 1.5 games. The Celtics basically played that series minus the 5th best player in the league last year.
The Cavs' salary situation made it such that they couldn't upgrade at all in the offseason. Their bench is about to be Derek Rose, Iman Shumpert, Channing Frye, a 37-year-old Richard Jefferson, Jose Calderon, and Jeff Green.
The Celtics essentially swapped Avery Bradley and Kelly Olynyk for Gordon Hayward and Marcus Morris, then swapped a cooked Amir Johnson for Aron Baynes. Meanwhile they got an injection of youth to their bench (Yabusele, Zizic, Tatum, Nader) while some of their young players are now one year more mature (J. Brown, Smart, Rozier).
Seriously... Why the assumption that the Celtics are destined to lose in the ECF once again? Lebron is a great player, but he's from infallible and he'll be 33. The Celtics should be favorites to come out of the East, assuming Isaiah's hip is intact.