Most likely it’ll be an adaptation of the tournament arc, or one of the other two things you mentioned. I am just so glad more Nanoha is finally coming. I knew this franchise wasn’t dead, and they’d give us something to hold us over before Reflections (if it ever gets made and released).
I like surprise announcements that suit my tastes in media.
A new website opened revealing a poster for a new anime by the creators of the Magical Girl Lyrical Nanoha franchise called Vivid Strike! Cast members of Nanoha Vivid will be returning. However, it is not yet known whether this will be a continuation of the Nanoha Vivid anime that aired in 2015, a Vivid spin-off or a brand new anime that takes place during the Vivid timeline. Vivid Strike! is set to air sometime this Fall.