Yeah, I was a 40-year-old dad when I was raiding top 30-50 US, and several of my guildies were in a similar age bracket. It was those young whippersnappers that were terrible at the game and had zero patience for learning/progressing.
Honestly, if I didn't have a wife and kid, I probably would've raided even higher level but taking care of the family didn't allow for a flexible playing times that those guilds would required. That was basically what was fun about our guild though, we were mostly middle-aged men and women with full-time jobs outside of WoW that were good at the game and limited time to play.
Honestly, I wouldn't be surprised if the average WoW player's age increased over time at a similar rate as the age of the game. Of the players I know that still play WoW, they almost all started playing between vanilla and WotLK, very rarely are they youngin's.