At this time, Apple is not listing availability of Privacy Screen Protectors for the iPhone 18/Max. The Privacy Screen is polarised; while speculative, it is highly likely that this will interfere with the iPhone 18's FaceID system that operates from behind the visible iPhone screen.
By contrast, Apple's product page for the standard Belkin UltraGlass 2 Screen Protector states availability and compatibility with both the iPhone 17 Pro/Max and iPhone 18 Pro/Max:
Belkin UltraGlass 2 Screen Protector for iPhone 18 Pro | iPhone 17 Pro
Whether or not a Privacy Screen Protector for iPhone 18/Max will ever be released is unknown at this time.