I'll believe in them building a third runway when I actually see it....and even then I'll bet it's too short, and pointed the wrong way, to be a great deal of use. The master plan may mention extra runways, but then so did my Melways a million years ago.
As for this event...I haven't read the ATSB report, but only the rather hysterical one written by Ben Sandilands. The 777 would seem basically irrelevant to the event. If the 737s were spaced with some form of stagger, as they normally are, then a collision is unlikely. Nevertheless, infringing the separation standard is quite possible.
I don't understand the comments about minimum heights to overfly the terminal...never heard of them. What does exist is a minimum height for a radar heading, but even then the heading can be accepted with the aircraft providing the terrain clearance.
Parallel runways won't magically make this sort of issue go away, as you'll very likely end up with operations like San Francisco, where simultaneous operations happen off the crossing parallels (i.e. four crossing runways, not just two).
At the end of the day though, simultaneous landings to crossing runways is a dumb mode, and always has been. Not using this mode would most likely reduce Melbourne's capacity dramatically. The airport, like all in Australia, is poor, and little, if anything, is being done to fix it.
