@hm -- us (#3):
both the fall of the (Berlin) Wall (Nov 9, 1989) and the German reunification (Oct 3, 1990) are singular events in (or probably rather, consequences of) the process termed "die Wende". The Monday demonstrations in the German Democratic Republic throughout 1989, eg, would be another constituting part of the "Wende". Thus, translating "die Wende" just by one of your phrases simply would not be correct. (Sure enough, these phrases will serve perfectly well in other context, especially when used to indicate a "before/after" date or the like.)
I wouldn't be very surprised if there were no idiomatic English expression at all for the "Wende", at least not yet, in view of the comparatively short time that has passed since then.
However, there has been a suggestion just to keep the German word "Die Wende" (in a previous discussion - Siehe auch: die Wende
(AFAIK, there are precedents for this idea, eg the "Ostpolitik".) I for one wouldn't mind if things would turn this way. I do like this idea.
"The Turn" rather is an ad hoc suggestion inspired by the wikipedia page cited in #2. Maybe I shouldn't have boldly entered it under "Übersetzung"?!
Good night ... oops ... good morning already?!