Thanks for posting this! How interesting.
I don't think it's safe to assume that it'll be direct-to-video at all. I believe Toho is an important Japanese film production company and I would be surprised if they didn't release the movie in theatres in Japan.
We shouldn't forget how different the Tamagotchi market is in Japan compared to the rest of the world. Interest there is great enough to make movies that would be fairly successful.
As to its quality, I don't know - I don't get many chances to watch Japanese movies about Japanese pop culture icons. I saw the Yu-Gi-Oh! movie (I got a free pass from work) and I can safely say that it was
awful, but then again, I don't think much of the card game or the television show. (I don't regret going though, because I heard one of the funniest lines I've ever heard in a movie: "But eternity didn't last forever."

) I know that I would really enjoy downloading and watching a Tamagotchi movie, if it were subtitled (or maybe even if it weren't!

Caption contest, anyone?

)