Yes, however it depends on the type of GTA Firewall system and GB-OS version. All firewall appliances will continue to function regardless of which version of GB-OS they are running. Customers running GB-Ware will need to be running GB-OS 6.2.12, which will be released before the GTA servers are shutdown. If GB-Ware customers do not upgrade to GB-OS 6.2.12 those system will cease to function when the GTA servers are no longer accessible.
All firewall systems must have valid registration activation codes in order to function. You should insure that you make a backup of your configuration and store a copy of the activation code offline. There is a separate FAQ topic addressing subscription features.