The existing (unmaintained) TS3 add-on has worked great for my gaming community, and if a new version were created, I would hope to see it continue the same features at a minimum. I also agreed with the development roadmap that the existing TS3 add-on's developer shared at one point (I can't find it right now), specifically the planned ability to assign channel groups according to forum permissions (not just server groups).
It's the assigning of TS3 groups according to forum usergroups that has been enormously useful. We have a rank structure and no one has to worry about manually assigning permissions on the TS3 server. For example, if an applicant is granted membership to the community, TS3 hooks them up with everything they need automatically; same if they're removed.
I am mostly concerned with the possibility that the existing TS3 add-on might become incompatible with future versions of XenForo. New features are secondary in my opinion.
If someone were to commit to a developing a new version, I'd prefer that they simply charge a premium price for a usage license. I'll contribute to crowdfunding if it is necessary to get the add-on off the ground and the developer looks credible, but it would be nice to avoid the drama that could occur if anything goes wrong with the development timeline.