After almost two years, the movie was finally released in Japan! Unfortunately, the movie released in a horrible time(The coronavirus outbreak) which may affect the box office. Some of the cinemas in Japan are even closed now. Let's hope everything is just fine ever after.
Another thing, there's an interesting Twitter account called @ShirobakoScript which is approved by Mizushima. I read some of them, it looks like describing some trivia of the anime. There are still lots of things can write to I guess.
(Translate: While checking on the Wiki, I just thought that, "Hey Wiki, check the official!")
Finally, although it may take some times for the English version, I believe that it will finally be released-- For both legal or illegal means.