They don't have to - just would be a nice touch - they don't even need to announce anything - just play a track as they come out, that's all; it's not scouse meltdown.
Yes - lots of great and talented people like Lemmy die. In turns of fame, prolificacy, inspiration and improtance culturally, he was on another level altogether, as was eveident on Monday.
The Club are of course under no obligation to do anything, just would be a nice touch and find it hard to believe people would begrudge it.
Again though why as they come out? I think regardless City would have a few Bowie tunes going pre match/half time which is what it should be restricted to