Even so, it might not be bad to provide a key to skip to the next file
without exiting query-replace.
Another problem I have with `Q' is that it requires typing `!' in every
file to replace all occurrences. So if I want to replace all occurrences
in ALL marked files at once without a query, I need typing `!' as many times
as there are marked files.
Maybe, when started by `Q', query-replace should apply `!' to all marked files,
and a new key `Y' should replace all remaining occurrences in the current file,
and a new key `N' should skip the current file as Miles has already proposed.