The only way I could see "technology" solving this dilema is if high ISO quality got so good that it was indistinguishable from lower ISO's - then you could jack up ISO to use f4, and get the same image with less weight and cost.
Unfortunately, I just can't see that happening,...because any advance in technology that would make ISO 6400 just as good as ISO 3200 would also probably make ISO 3200 that much better as well. And, under those circumstances, we'd probably still want to shoot at f2.8 to get the even better low ISO performance. I could see some amatures making the compromise to save money, but pros will always want the fastest glass to use the lowest possible ISO and get an adequate shutter speed. A lot of shooters also like the brighter f2.8 viewfinder, and improved AF speed with a max aperture f2.8 lens in bad light.
The 70-200 f4 is a great addition to the Nikon catalog, that IMO is about 15 years overdue. I wish they'd make a cheaper version without VR for us indoor sports guys like Canon does. But, it's not a substitute for f2.8, and it certainly doesn't obsolete it for many of the reasons people buy f2.8 zooms.