The question answers itself, because the 16-year old tech geniuses from 2006 have become the 23-year old tech geniuses of today. Presumably any "tech genius" will become more genius as they grow older from 16 to 23. So today's 23-year old whizzes should always be superior than today's 16-year old whizzes. And after another seven years, some of today's 16-year olds will become 2020's best 23-year olds, and should outshine 2020's best 16-year olds, who won't be 23 until 2027. The better question to ask is, at what age is person going to peak in technological ability?
The bigger fallacy is who enters these competitions? They might attract exceptional high school students looking to distinguish themselves in their college applications, but your best college/university kids and young professionals are going to be too busy with other ventures and commitments to participate in these contests and hackathons. If you've got a million-dollar idea, you're not going to waste a weekend on a contest that can net you a couple of thousand dollars.
In reality, most of the young professionals participating in these events are either unemployed or underemployed. They're hardly the best representatives of their generation's talent.