I'm 28 and I started playing FFXI when I was around 21 or 22 years old. Great times for my first MMO.
Anyways, it definitely seems the average age of FFXIV players will be in the mid to late twenties, which I guess you can attribute to many making the switch from their FFXI roots. That's at least the story for me.
I have an uncle (by marriage) who's a dentist. He's probably in his early to mid fifties at this point, and he's a hardcore Warcraft player. When I was visiting that part of the family (which I haven't seen in years), he comes into the house, politely says his hello's, grabs a stack of a cookies, a tall glass of chocolate milk and disappears upstairs. Hour or so later, I'm taking a tour of the house when I spot him posted up at his computer desk with a head set on, playing some Warcraft.
Elvaan: Warrior75, Bst74, Rdm64, Pld45, Whm42, Nin37, Thf37, Mnk37, Blm37, Drg32, Dnc32, Rng5