Can I keep using my Xbox One offline indefinitely without updating (after updating this one last time)?

Solution 1:

The Xbox OS that original Xbox One uses is still the same OS that the new generation of Series X|S consoles are using(which is probably the OS update that NHL 21 would be asking for). They can be played offline without any issue.

However, Kinect has been deprecated. The Series X|S are pretty incompatible, whether an OS Update solidified that or just hardware (the consoles do not have built in ports) is unknown. It may still function, but Xbox/Microsoft no longer support it and have it placed firmly in "end of life", so if an update does "break" it, because it's not tested for compatibility anymore. They don't have any obligation to fix it.