Latest updates for iPad mini 4

The iPad Air2, iPad mini4 can be updated to iPadOS 15.7.1 - but do not support iPadOS16.x. iPadOS 16.1.1 is available for these models of iPad:

• iPad Pro (all models)
• iPad Air (3rd generation and later)
• iPad (5th generation and later)
• iPad mini (5th generation and later)

While the iPad Air2 and mini4 cannot be updated to iPadOS16, when updated to iPadOS 15.7.1 they are fully up-to-date with available security updates.

Assuming that Apple continue to release security updates for iPadOS15.x - and they have continued to provide updates for earlier models of iPad only capable of update to iOS12 - you should anticipate ongoing security maintenance for the foreseeable future.

Unfortunately, that is the highest possible for the iPad Mini 4, as shown at: iOS 16 and iPadOS 16 are compatible with these devices - Apple Support