I think this is overly optimistic. At least until Sullinger demonstrates that he can stay in shape, play big minutes every night, not average 5 fouls per 40, and that his back isn't an issue anymore (all these are legitimate concerns). h, and stay off the three, because it clearly isn't his shot. And even so, I'm a bit skeptical about whether an offense, spearheaded by Rondo/Green/Sullinger can be league average.
I think what we need is a real two-way big man, who can push everyone in our big man rotation where they belong (that is, one notch down). Then again, who in the NBA doesn't need that.