Did Britain make its own large pre-dreadnought fleet obsolete by launching HMS Dreadnought?
Short answerNo. Dreadnought changed the standard, but Britain retained numerous useful pre-dreadnoughts for years, including during the First World War.
NotesBritain still had a large force that included capable pre-dreadnoughts, and that their operational value did not disappear in 1906. Even during the First World War, an older battleship could remain dangerous in the right circumstances. The point is a corrective to the popular shorthand that every pre-dreadnought was instantly obsolete.