At any rate we're bringing this waaaaaay off topic. Bottom line is, Miki's going to be leader once Yossi leaves. Whether people think she's suited for it or not of if they think she deserves it or not, that's how it's going to be. Nothing we say here will change the fact that MM will soon stand for "Miki's Musume". 
Actually, discussing about Miki becoming the new MoMusu leader is not necessarily off topic because it's related to Yossie's graduation; in fact, it's a direct side effect of Yossie's graduation since Yossie is also MoMusu's present leader.
Also, discussing about the changes in MoMusu's image due to Yossie's presence or absence in MoMusu should also be on topic, I think, since every graduation always brings about some change, be it big or small, in MoMusu's image.
But anyway, Miki's case is quite a complicated and controversial issue, whether she's suited to be leader or sub-leader, or whether she should have even joined MoMusu in 2003 and not continue as a soloist are all controversial topics. But one thing for sure is that Miki's Musume would most probably become quite different from Yossie's Musume, let alone Iida's or Nakazawa's Musume.
But in any case, after all is said and done, whatever we fans get to see of MoMusu is decided by powers beyond our control, i.e. Tsunku, UFA, and other powerful people in the Japanese Entertainment Industry; they are the ones who have the final say, while we, the fans (both inside and outside Japan), and the MoMusu members themselves, can at most suggest or request or beg...