I think there should be a point of clarification for those not as familiar with the AtariVox and Stella: While Stella can't internally generate AtariVox voices, Stella can drive an actual AtariVox plugged into an interface like a re-flashed 2600-dapter II (you can order them already flashed for the AtariVox). You still need to plug an external speaker into the AtariVox to hear the voices, but it will work fine. I use this setup with Stella on my Mac all the time. Whether the 2600+ could eventually drive an AtariVox is a different question. So Stella does support the AtariVox, but it cannot emulate it.
As an aside, the SpeakJet chip used in the AtariVox is no longer in production. However, according to this post (confirmed here by the SpeakJet's developer), the SpeakJet is internally a PIC18F1320 which is still in production. So more chips could certainly be made (I don't know if this is an issue or not - I'm unaware of what sort of stockpile AtariAge has). The SpeakJet is one of those IPs I'd love to see Atari acquire so that the AtariVox could (potentially?) be emulated, and have them (or Plaion) design and sell a new AtariVox that has its own built-in (magnetically shielded) speaker, designed to aesthetically to go with the 2600+ (and of course, original 2600s).