It's academic now, but I did once ask what would eventually happen to Aris, as the only Sumatran there, and was told he would stay at Monkey World. I had the feeling I was speaking to the wrong person. I'd have thought the MW nursery was only a temporary home for youngsters placed there from other zoos.
They've said Gordon has a home there for life, but they've got some valuable genes in their rescued orangs. But there are limited places in zoos for orangs (eg nobody seems to want Tiga at Twycross), and the rehabilitation centres in Borneo and Sumatra are running out of safe places. It's a huge dilemma.