A bit less than 50% of the whole Internet.

Wow. That's so amazingly unpopular. Why anyone bothers talking about something untold millions of people use every day is beyond me.

It’s not flat: https://www.google.com/intl/en/ipv6/statistics.html

You have to take into account seasonal trends. The summer is always higher, so yes, we’re currently below last summer, but we are above last April 1st, and this summer will be higher than last summer.