I would never say never but it would be a fundamental change and one perhaps too far right now. The changes over the past few years have been huge on the surface but not changed much underneath. It's still the same top down hierarchy. It's still insular, protective and secretive. Money is still flowing from congregations to head office.
The issues over equality and prejudice are major. If they were to rent space out I am sure that there are dozens of ex Witnesses who would be lining up to request space for any organisation whose presence would embarrass the WTS. Do you see comments boxes or even email addresses on jw,org? That tells you how open they really are.
The dedicated building is also a factor.
The only way I can see them opening their doors is if refusing to do so meant they could not attract charitable tax status.