(for the tweet show up for now the workaround is to replace the url with twitter .com)
that interview (if i'm not mistaken, is a Famitsu one from some months ago related to PokeMiku) needs a bit more of context: in that part, Wataru Sasaki of Crypton explains a bit what led to the development of Project Sekai on mobile devices instead of a new Diva. At the time of Sekai announcement, they also explained that they made that to celebrate the fact that the first Diva was on Psp, so together with the release of Mega39 on Switch, it was the best option for a mobile experience.
And to be clear, in that interview he never says "no more Diva", but underlined what I said many times: there were some concept titles after Diva X, but the main difficulty of Project Diva (and any music game in general) is the cost of music licenses, the balance of development costs and the number of included songs. For example, Project Diva f and Diva X were very expensive to make for having brand new songs and new PVs. Also, Sega changed its headquarter building to have a more unified development of its titles. For example, some members of Diva team helped with development of Sakura Wars and Valkyria Chronicles 4.
the sales in total, thanks to good fans feedback, were very good, in fact Project Diva series sales are on same level (a bit more) of Persona series (you can check Sega financial reports), and both Mega39s on Switch and Mega39s+ on PC exceeded Sega expectations. I remember the first week in Japan, the retail copies of Mega39s were sold-out and Sega needed to make more copies.
After the release of the PC version, one of Diva producer said that he wants the next title "to come out naturally". And I personally know that the main task is to find something that can be so enjoyable for the fans and also not very expensive (the problem of having 20-30 songs setlist from famous producers). Some concept ideas might be a party game with many minigames, or a complete PV Edit game that will allow to make PVs without the limitations of PV Edit of Diva f-f2nd series.
there is also Project Sekai for PC (and ps4-ps5-xbox-switch 2 under planning) in development at Atlus, and SEGA CEO himself said that he plans to release portings and remake of Sega most famous IP. If you know Persona, you know that during these past years there have been many different titles released, and as I wrote earlier, Project Diva series sales are even higher of Persona. I would love a collection of Miku titles, for example collection n.1 Project Diva PSP titles, collection n.2 Project Diva f-f2nd-x, collection n.3 Project Mirai series <3