They better be following up on that concept movie and give us Holy Mami. Just another step to making the quintet their own pantheon.
That was actually the one concept that I wasn't a fan of from that teaser movie.
Implying that they want Mami to be the biggest opposition to Devil Homura feels more like fanservice than anything else. We already got our big Homura vs Mami fight in the previous movie, and there really isn't much that ties the two thematically.
My Sayaka vs Homura headcanon hope is, admittedly, also fanservice, but also works on a thematic level and follows up beautifully with what was already shown in Rebellion (the Madoka series has some fantastic symbolism and imagery, but it can also be
blunt as hell with the symbolism when it wants to be).
Their relationship is also the most under-explored in the series and just serves as the perfect catalyst for their encounter: They both share a common goal in wanting to protect their best friend, but they also carry the extreme opposite ideals that Madoka strove for.
It's the perfect kind of rivalry, because neither are entirely wrong and their end goal is almost the same. That's why I'm hoping for something that's both a beautiful kick-ass fight scene but also filled with a lot of heartache and idealistic discussions. The kind of stuff Urobuchi is best known for.
It would be real disappointing if they tossed aside that concept for "Let's just give Mami bigger guns".