Think of the processor as two products
The audio engine handles decoding, bass management, routing, room optimisation and level control. The HDMI subsystem handles switching, EDID, HDCP, HDR metadata and video bandwidth. Those two parts can age at very different rates.
A mature processor may remain acoustically excellent while lacking 4K120, VRR, QMS or the bandwidth required by newer sources.
Bandwidth is only one part of HDMI compatibility
40Gbps and 48Gbps headline numbers matter, but so do HDCP revision, EDID handling, eARC behaviour, gaming features and the exact formats supported on each input and output.
A specification that says “8K” or “HDMI 2.1” is not enough to understand the real signal path.
External video switching can decouple upgrade cycles
In some cinemas, sources feed a video processor or matrix before audio reaches the AV processor. That can allow the audio processor to remain in service even when its internal HDMI board no longer matches the newest source requirements.
The trade-off is more complexity, more handshake points and a need for careful audio extraction and lip-sync management.
Plan the likely sources before choosing a processor
A cinema built around movie playback may have very different HDMI requirements from one that includes current-generation gaming PCs or consoles.
Specify the actual source formats, display chain and expected upgrade cycle instead of buying HDMI capability as an abstract checklist.
Useful official references.
Product features and software capabilities can evolve. Check the current manufacturer documentation for a live project.