But the Mental Health Minister says no-one will be left behind in the transition to the new services.
The comments come after announcements a major redevelopment of the hospital will begin next year, to equip the troubled ward 10 to be able to meet more modern needs.
Ward 10 had come under fire from the Office of the Ombudsman in two separate reports, which outlined the lack of resources for patients and carers, the outdated setting and the lack of solitary space.
Then-chief ombudsman Peter Boshier deemed ward 10A "not fit for purpose" and a "volatile environment".
Sharon Peterson, of Gore, said her son had serious needs.
"My concern is the sheer disruption.
"My son cannot manage in the community. When things go to custard, they need a stable place for him or the others to go. They need the infrastructure.
"I’m worried he could end up homeless."
She met Mental Health Minister Matt Doocey in Gore earlier this week.
"I got the sense that he was going to do everything in his power to ensure there would be a suitable place for my son.
"But I can’t be sure that will definitely happen, because of everything that has happened in the past few years."
A spokeswoman for Mr Doocey said he assured her ward 10 would not be closing without an alternative, safe place for the patients to go.
"The minister made this expectation clear to Health New Zealand."
Health New Zealand southern interim group director of operations Craig Ashton said in a statement redevelopment work on Ward 10a at Wakari Hospital was expected to start later this year.
"Plans are in place to ensure continuity of care for all patients at Wakari Hospital while this work is carried out. Further details are still being finalised and will be available in due course.
"This redevelopment acknowledges urgent work needs to be undertaken now on Ward 10a while detailed planning for more substantial investment takes place."
