The Showa, Heisei, and Millennium eras of Godzilla movies are defined clearly by things like continuity, staff, designs and the like, as well as the fact that they were turned out regularly with the usual one-a-year pace. They stand out so clearly in the minds of us fans that we tend to think of the entire genre as adhering to those divides, even if, if you think about it, in terms of the genre as a whole the Heisei and Millennium eras are really one big era when kaiju movies were produced fairly consistently for about 20 years (the Heisei Godzilla movies, Yamato Takeru, The Gamera Trilogy, The Mothra Trilogy, the Millennium Godzilla movies and ending with Gamera the Brave).
But now I feel like Toho's era of consistent eras is over. Both Shin Godzilla and Godzilla: Monster Planet strike me as similar approaches: established talent in charge, radically reinventing Godzilla. What if this is the new normal, and an ongoing Godzilla series building on the same continuity with the traditional format of Godzilla taking on successive opponents a thing of the past? ... at least in Toho's case, because that's exactly what Legendary's MonsterVerse films are doing for a world audience, including Japan (and fulfilling Toho's decades-long dreams of concurrent foreign and domestic Godzilla movies).
Instead of an ongoing series, each Toho Godzilla project may be conceived as a self-contained project, and after following a live action movie with an anime trilogy I'd say every factor could be in flux for future Toho Godzillas. Maybe the next Toho Godzilla won't even be theatrical, but a TV drama? Personally, I find this approach pretty exciting. I don't think the Heisei series being continuity heavy really added too much, and the Millennium series' goal of no continuity done-in-ones was a bust because the movies tended to not take advantage of the freedom. Really, aside from GMK how easy would it have been to make the rest of those movies in the same (loose) continuity?