Well, most core router hardware is advertised to work at higher speeds than the actual backbone speed of 10Tbit/s (40 in some places) ... and IOS and JunOS are both IPv6 ready, so it's certainly not a big deal for the big boys ... they'll just add more hardware if things slow down.
What the rest of the world will do, you're probably right. I suppose they would've at some point anyways.