I think it's more of a "you should have kids/be spending all your time with your kids in your thirties!" thing more than a "you shouldn't be playing games in your thirties" thing. So if, ten years from now, the average age for childbirth has not increased, we may still be seeing this kind of prejudice.
Good point. Time does march on, and human activity is not age-invariant, especially after age 120.
This is also a better hypothesis because it has better explanatory power: The Today show is predominantly watched by people who are not scrambling to get to work in the morning, and that group is going to contain a high percentage of people with kids, and such people think like... people with kids.
