It just proves Gaga releasing music is an event, which it is. It also means she has a massive fanbase, which she does.
I can see Gaga debuting with everything from 400-600K first week with her next lead single. It really depends on the sound of the song, when it's being released, and her press situation at the time.
Actually Gaga's team should definitely utilize spotify and the other streaming sources so that it goes number 1 in the first place LOL. But I do agree with Tim that debuting number 1 isn't all that important. It can front load the sales.