Cinderella Girls or Million Live, neither of them will be the same thing; but why'd I say that Cinderella Girls is more likely to take the torch? I have a reason, and it was formed under observation.
Mirai, Tsubasa and Shizuka, although they're 'titled' as the main trio, but they've never sing together since ML starts to release albums, there's no obvious connection between them. Haruka, Chihaya and Miki, on the other hand, although there's no exact unit designated in the game or in the anime, but at least they have sung songs together for many times, they also have strong connections to each others.
The main reason for me to believe that Cinderella is going to take the position, is the close friendship of the main trio like the original trio; they entered Mishiro Production at the same time, arranged into one unit (take note that 'New Generations' already exist in the game,) do lessons and stuff all together. While ML trio acts more scattered and not even forming a unit since their debut, the social chain in ML seems blurry, not like what we've seen in the original group or Cinderella Project - at least in the new CG anime, but that's how I know.
Don't take this 'passing the torch' thing mindlessly, because it is important to get the right person to take it. But since they all belong to Project iM@S, if you're going to say '765PRO should only pass their torch to their direct juniors, not to a group from a different agency' I won't reject, but bare in mind that CG has a more solid foundation than ML does.