And 5 respect points?
Do you think this is a good idea?
And 5 respect points?
Do you think this is a good idea?
I'd think not. First, I'm not sure it's even possible with the Stack Exchange software to do that... But I'll leave that to an SE person to answer.
Badges are used to encourage behavior beneficial to the site. Trying to time your question to be a certain question number isn't (at best, it's neutral). And would you want to award a badge if it turns out to the 100k question is not a good question? Or what if it's by a not even registered user?
Badges are also, with the exception of the beta badge, something everyone can earn. The folks who got the site going in beta did something important, so that's justifiably different.
Finally, badges are because you accomplished something, you earn them. But asking the Nth question isn't something you've earned, you could have just stumbled across this site and its your first question. You didn't really do anything to earn a badge—it was the work of everyone else collectively that created 100k questions.
Celebration is probably in order, but giving a random lucky person a badge isn't the way to do it. It's an accomplishment of everyone working together, of the site, not of an individual.