I understand the thinking and I sympathize with the economics.  Even with upgrades that cost a good fraction of the cost of the original software, your existing user base is not your primary source of income.  It's the new users you can entice -- and for them, more eye candy is the draw, not the grumblings (or relative lack thereof) on specialized forums.

And don't get me wrong, as such software goes Carrara is one of the most stable out there.

There is, however, a disturbing tendency in their bug-stomping efforts.  Not just that priority goes towards anything that interferes with importing V4, but that anything used to make decent export-level models is considered not important enough to even talk about.  Just by seeing what is most active on the bug tracker, one gets the strong impression that the software is being staged primarily as a content renderer.