We have Vocacolle stats again for Summer 2023!
I was curious about whether Teto would impact Japanese producers, I saw a great deal of excitement for her from nostalgic English-speakers, but I wasn't sure if that success would translate to her core market. Based on this chart, it definitely has. There are a few other small changes as well - people buying SynthV for Teto naturally gave Mai a little boost too.
Source
Summer 2023
The most used vocal synths of Vocacolle, translated:
1. Hatsune Miku, as always
2. Kafu
3. Kasane Teto
4. Flower
5. Kagamine Rin
6. Chis-A
7. Kagamine Len
8. Hanakuma Chifuyu
9. Gumi
10. Koharu Rikka
11. IA
12. Natsuki Karin
13. Mai
14. Sekai
15. Rime
Note that due to the sample size there isn't a huge difference (if any) between say, Flower and Len, or Gumi and Karin. So I would treat most of those below the top 3 as in no particular order.
SynthV seems to have made rapid gains in Japan, Vocaloid is still definitely the most popular, and it's fun seeing the top 3 now represent the 3 main engines.