I think you’re referring to the delays on digital and/or analog input channels and you’re not referring to delays on ARC?
Unfortunately I do not know when a firmware will be released (I’m not on the development team). It seems updates are on its way as announced in this post.
I inquired about the status of the issue in the TS and a similar issue (Async Issue with all digital inputs, ref#85). All I can say is Arcam is aware of a latency issue in the audio path. I don’t know if a fix is on the roadmap and when it will become available.