Yes, because the inside is being totally dismantled and then there's a complete renovation . And there are historical elements that have to be protected and handled with care, so this will slow things down ...
The restauration will 'completely' be finished by that time, meanwhile you can not visit the Town Hall. Maybe some parts will be open earlier, but I could not find specific information.
See: (only in Dutch) antwerpen.be / dossier / restauratie-stadhuis - without the blanks since tripadvisor does not allow to add links
Get quick answers from Town Hall (Stadhuis) staff and past visitors.