^I feel sorry for Risa too, but the truth is, Ai is actually an aberration when it comes to being centre and leader at the same time. Previous leaders generally do not take the central role (Nakazawa, Iida, Yossi -- I'm leaving out the others -- all of them tended to be back in the background). With Ai, she was already in the midst of things when she took on the role of leader, so yeah.
Though I must say, Risa deserves to take a more central role. Lord knows she has worked hard enough, and she is very solid performance-wise. Regardless of how I might personally feel about her (she's not my favorite, and is unlikely to ever be), I think she really does deserve more than what she gets.
But it doesn't surprise me that Riho gets pushed to the front. In a way, it makes sense -- they need to establish one of the younger ones as a semi-permanent fixture where it counts, since graduation might still come to any one of the senpai members in the discernable future. What interests me will be who takes over Ai's place once she leaves; if Risa gets passed over that as well, that's when everyone, fan of her or not, should get pissed.
I have this feeling Sayu is next in line for center...noooooooo!!!