I can’t help you with any insight into NAD schedule.
Playing Devils Advocate do you expect a major breakthrough in amplification technology from any company making AVRs or Processors? The major development switching to Class D a decade or so ago hasn’t been followed up with anything new, by anyone. Amplification technology is relatively stable especially compared with streamers, DACs and other digital technologies.
The major changes in HT will be features. Immersive sound, touchscreen, integration of Apps….I am not surprised that a new model AVR sounds like an older model. If the new feature lineup fills a need, then make the change. If not, I would sit tight