I find this notion interesting.
I am a manager. I have hired people over 50. On my team right now I have 3 people within 3 years of full retirement. One of whom I hired within the last year. I also have two that are within spitting range of 50, one of who I hired less than 6 months ago.
When I'm bringing someone on board in the 40+ category with 20+ years of professional experience, I have drastically different expectations than what I'm looking for in a 24 year old kid who's on his first salary gig out of college.
I'm looking for someone who understands corporate structures, workflow analysis, generalization. I'm looking for someone who says, "When you boil this down, it's an asset management system, and I've worked with half a dozen different vendors and 4 different home grown systems that do the same thing". I want someone who can sit down with users, look at what their doing and not just imagine up a new piece of software, but understand the business process to the point where they can make truly business impacting recommendations with a realistic grasp of what it would take to accomplish. I want someone who will pull the young bucks aside and explain to them the merits of simplicity and maintainability, someone who can do code reviews without being a pretentious dick, someone who can help guide that next generation of developers into the future engineers and architects I need.
People over 50 absolutely have a place in the development arena. But if you're 50 years old and still expect to have the same responsibilities as a 24 year old kid, you will be sorely disappointed.