You're right, Frala was the first of the three females to breed at Taronga Zoo. She had a male infant in 1998 that lived for 12 days and a stillborn female infant in 1999. Frala was the only female not on contraceptives. Frala was put back on contraceptives in 1999 but her and Mouila were taken off contraceptives in 2002, which led to the births of Fataki and Mbeli in 2003. Following Frala's births, Kibabu would indeed pay extra attention to Frala and ensure she had space from the rest of the females and their offspring so she and the baby could get the rest they needed. Mouila has always been his favourite however.
Dublin have indicated they have no plans to bring in a new silverback- at least presumably this refers to the several years Lena has a small baby, after that they might add a younger male. There are three groups in Europe with currently no silverback; Dublin, Munich & Kolmarden, while Apenheul may be planning to re-organise their group too. None of these seem in any hurry to add a fresh male though. And there are also something like 65 males in bachelor groups in Europe too, though many/most can be discounted as potential group leaders on the grounds of being from over-represented lines. A few of them, and like Ganyeki at Werribee, do have low representation on one parent's side, but not the other.