well, back in the series, I like Ranka not because I know in advance that she is the main heroine, but it is because that I like Ranka during the series...to me, Ranka and Sheryl are co-lead in the series...just like DYRL, Misa and Minmei both were the main heroine...
Now I don't know how Ranka got treated in the first movie...but I won't believe too much about what other posters described in the forum...at least not this forum...(this is Sheryl's land in animesuki XD) I will hold judgment until I see the first movie...besides, the first movie, based on it's name, is focused on Sheryl, so even if the first movie is really focused on Sheryl, I won't worry too much
So, calm down, and we shall see
Btw, there is a Ranka's forum
http://bleachasylum.com/showthread.php?t=7790
and those posters posted a lot of beautiful Ranka pics there, I really recommend Ranka fans to join