The Mosgiel-Taieri Community Board chairwoman said the imminent closures had come shortly after a ''massive fundraising effort'' to support the redevelopment, completed in 2015.
''It's a real shame for the community,'' she said.
There was some uncertainty about what would happen with the Mosgiel RSA, including the use of its Church St building by other community groups, and the building's longer-term future.
The Mosgiel RSA played a valuable support role, including in providing a venue for non-RSA members, she said.
Mosgiel RSA chairman Major Peter Amyes announced on Monday that the restaurant and bar could not continue to trade unsustainably.
An information evening for members will be held on May 13, and members' consultation meetings are scheduled for May 22, 23 and 29, before a membership vote on the club's direction.
Age Concern Otago falls prevention co-ordinator Margaret Dando said about 80 people attended four falls-prevention classes at the ''excellent venue'' each week.
It was likely the two Tai Chi classes would have to switch to a different venue after the RSA restaurant closed on May 11.
Two other Steady as You Go classes would continue until June 30.
It ''would be great'' if they could then continue, but that was unclear, she said.
RSA Dunedin president Lox Kellas said it was ''sad'' that the restaurant and bar were closing, and noted the Mosgiel building was also a venue for other groups.
Mr Kellas hoped the planned consultation with members would lead to a ''satisfactory outcome''.
Maj Amyes realised many people were feeling concerned and frustrated after Monday's announcement.
He was also ''sad and frustrated'', and he felt for everyone who relied on the RSA, but change had been needed.
The RSA wanted to continue to help non-RSA members, but the situation after June 30 was yet to be decided by club members.
