The Holy Father has accepted the resignation of the rights and privileges of a Cardinal, expressed in canons 349, 353 and 356 of the Code of Canon Law, presented by His Eminence Cardinal Keith Michael Patrick O’Brien, Archbishop Emeritus of Saint Andrews and Edinburgh, after a long period of prayer. With this provision, His Holiness would like to manifest his pastoral solicitude to all the faithful of the Church in Scotland and to encourage them to continue with hope the path of renewal and reconciliation. LinkIn addition to "resigning" the "rights and privileges of a Cardinal", one can certainly be deprived of these rights and privileges and even the office and title itself (see c. 1336.1.2). As for O'Brien, I think it is correct to conclude that he is no longer a Cardinal of the Holy Roman Church even though the communique does not say this explicitly. If a Cardinal no longer has the rights and privileges of a Cardinal, what's left of the essence of being a Cardinal? Nothing, it seems to me: it doesn't make sense to have a CINO (Cardinal in name only).
Since this is such a rare occurrence and I know so little about it, I could be mistaken.
Update: Catholic News Agency has an article on this event, with the title "Pope accepts disgraced Scottish prelate's resignation from cardinal status."
Update II: Other news outlets are reporting that "the Vatican" has said that O'Brien "will retain the title" (here, for example). "Title" can refer to the rank of "cardinal" as well as to his titular church (Ss. Gioacchino ed Anna al Tuscolano). I would be interested to hear what the people of that parish think if their titular Cardinal is now a "CINO" due to grievous, moral failures.