With Bill Murray wading into whether there should be a reboot/sequel to Ghostbusters with all-female leads, I figured I'd just share my thoughts on why the time for this idea is now.
Separation. Enough time has passed since the first two Ghostbusters movies that audiences won't bat a lash at new actors as Ghostbusters. Given how careers evolve, it would be shocking if the (remaining) original cast all wanted to return. It also frees audiences from maintaining expectations that this would be a straightforward continuation of the existing story.
Characters. The original Ghostbusters consisted of a Dreamer, a Scientist, a Charlatan, and a Working Stiff. Female leads open this up to a slew of new characters or combinations of characters. As long as the stupider stereotypes are avoided, it's a goldmine.
Practical effects. Digital effects have done great things for movies in countless genres and there is no way that Ghostbusters would be without them, but in the last couple years, audiences have been calling for something more. The return of practical effects, in combination with digital effects will give the combination of visceral and campy that made the original Ghostbusters feel so on the mark.
Diversity. Diversity offers a chance for more developed stories and wider appeal. This shouldn't be limited to switching to a female cast. In the right hands, giving characters different backgrounds will make the movie funnier.
We're ready for it. This will seem superficial, because talented female comics have been available for ages, but buddy and ensemble comedies starring women are gaining enough traction to make the movie a commercial success. Combine that with Ghostbusters and the movie is an obvious choice.