This is definitely very sad news for me personally. In the last few years, I've read the Holy Father extensively. I admire his traditionalist viewpoint, scholarly insights, and uncompromising opposition to relativism which mistakes personal penchants for religious practices, and individual ideology for cosmic truth. He and JPII are like two very close spiritual fathers to me. I am going to miss him very much.
At this crucial moment of the Church, which is but one of many in 2000 years of her history, let's pray for the Holy Father's personal health and for the Church as she awaits a new leader.
On a more cheerful note, as great as JPII and BXVI are, we know that Christ - not even St. Peter - is the Church's true rock and foundation. Surely there will be days ahead when we will be "sifted like wheat" (cf. Lk. 22:31), as Satan is prone to do throughout Church history. But Christ will be there to ensure she continue to battle well so that the forces of evil will never prevail (cf. Mt.16:18).