First, your hypothetical playoff seeding is a bit out of whack.
The Celtics may finish 4th, as they have a penchant for taking part of the season off and gearing up for the playoffs, but Indy is not finishing 2nd and the Bulls will have a huge uphill climb to finishing 3rd.
Remember, the Bulls will be without Rose until probably December and they ditched every SG on their roster (unless you still count Rip). They're also openly trying to trade Noah and Boozer.
Indy may finish 2nd, but there's no guarantee. They traded their starting PG. They're still young and they lack a closer.
If the Celtics stay healthy and focused, and their bench plays up to par, they'll have a terrific shot at finishing 2nd, which will match them up against the Heat in the ECF again.
And, if they meet the Heat again in the ECF, health and the refs will be the two biggest issues.
Let's not forget that the Celts had a 3-2 lead on the Heat in the ECF this year despite losing Bradley, injuries to Pierce and Allen, and the refs doing everything they could to hand the series to the Heat - Rondo's non-call, Pierce's fouling out (twice).
The Celtics can beat the Heat, if they're healthy and the refs stay the hell out of the way (which is no guarantee).