For those interested, and after an unnecessary amount of back and forth between Themeforest and I, Themeforest has now added the 3.x.x version tag to its collection of Ghost themes. (It also rather belatedly added the 2.x.x version tag, seeing how it hadn’t added tags for new versions since 1.18.x.) There’s more than a dozen there, although I see that there’s a few members-enabled themes that have yet to add the new tag.
I’ve personally purchased Nubia and Melaka (both updated for 3.x.x) by Aspire Themes / @ahmadajmi, which I can say both work fantastically and are very well supported. And here’s to hoping that Eston’s announced upcoming update is released sooner than later