Despite that the Bulls look scary, Cavs are clear favorites in the East due to the big ? over Rose. He could be anything between great and inactive. Now, given that it's Spurs vs. Cavs in the Finals, I'll take the Spurs 60-40. But Spurs have a way tougher road to even get to the finals, likely facing 3 tough opponents vs the Cavs who will only have to face 1. I guesstimated some numbers and estimated that they are about equally likely to win it all.
Say the West goes: Spurs OKC Clips GSW Mavs Rockets Suns. Spurs are only 80-20 to beat the Suns (or the Grizz) in my book, as the Suns will be boasting arguably the NBA's best backcourt. Or they could draw the Mavs who took them to 7 last year and have now added Parsons and Chandler, or the Rockets. Regardless, let's say an 80% chance of reaching round two. Now they're up against GSW or the Mavs in this bracket, both of whom will be better this year than last. I think 70-30 is pretty reasonable. Finally they draw Clips or OKC, both of which are likely on par with the Cavs. 60-40. By these numbers, Spurs have only a .8*.7*.6=34% chance of reaching the Finals.
In contrast, the Cavs have a cakewalk to the ECF if they win 1st seed (probably equally likely as the Spurs to do so). East could go: Cavs Bulls Wiz Heat Raptors Hornets Hawks ?Nets?. Whoever is the 8th seed (Nets? Knicks? Celtics?!) will be a total joke. Cavs are more likely to sweep than to lose that series, let's say 95-5. Second round is the Heat in this bracket, and I think LeBron will drop 60 pts in game 4 in Miami for the sweep. But all kidding aside, is Miami next year better than the Suns/Grizz? If Wade is healthy, they're a bit better, and if not, they're significantly worse. Cavs will be well rested; 80-20. Now ECF are anybody's game. I don't think Cavs are better than 50-50 against the Bulls with healthy Rose, but there's two other possibilities: (1) Wiz beat Cavs (40%), in which case the series is 60-40, and (2) Rose is hurt or ineffective but Bulls still make ECF (15%), in which case the series is 70-30. This adds up to .4*.6+.15*.7+.45*.5=57%, and overall a 43% chance to make the Finals.
Now, assume that Spurs are 60-40 favorites to beat the Cavs or whoever might beat the Cavs (likely a healthy Bulls squad), and that the Cavs are 50-50 against whoever might beat the Spurs (OKC or Clips). Then the Cavs and Spurs both have a 20% chance of winning it all.
TLDR: even though the Spurs will likely be better than the Cavs next year, the Cavs have just as good a shot at the title because the East is so weak.