Developers Lindholdt Springett - the firm with the contract to develop a £1 million replacement in Toft Road - said a number of companies had already shown an interest in the current site in Brook Street.
Partner Morten Lindholdt said the building was likely to become offices and would not be radically altered.
"What's certain is that it's not going to be knocked down," he said. "It's a beautiful building and a beautiful space."
The only part of the turn-of-the-century building under threat is the rear extension.
But any other alterations would be led by whoever bought it.
"At the moment our focus is on the new library," he said.
Councillors will meet this month to consider the new library, cafe, community centre and flats in Toft Road.
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