Is 11 people really a massacre?
Anyway, one definite effect is that the Mossad is going to have a lot less global cachet; from what I can tell, it was really Operation Wrath of God that put the organization on the map as "people with whom is not to be fucked".
The 1973 raids in Lebanon are butterflied, of course, which is going to have implications on the Lebanese Civil War (which will likely still happen), and may also have effects on a *Yom Kippur War.
And of course: no GSG9. In fact, elite counter-terrorism units may be delayed in a lot of places.