First, he notes that they have internal numbers that the majority of players don't yet have a level 80 character. This might be a known or assumed fact by some, but for many of us it's interesting to hear Blizzard extrapolate on the issue.
Vaneras goes on to point out an important tidbit – don't assume just because all your friends are 80 that everyone else is as well. People that play all the time tend to gravitate towards other people that play all the time, and folks that only log on once or twice a week gravitate towards each other as well.
This means that just because everyone on your friends list is 80 doesn't mean the whole server is yet. I know that for myself nearly everyone's main is either 80 or high 70s now, and most have alts quickly getting up there in level too.
But then I'm reminded of my brother, who just dinged 77 a couple days ago.
This is also good to know as it means battlegrounds and Wintergrasp will be filling up more as a greater number of folks ding. That's only going to lead to more fun for everyone.