Actually, if the average age keeps going up, the ability to spend time at the show should increase. Perhaps it's other factors such as (1) having enough trains, (2) developing other interests, (3) tight money, etc.
The average age definitely will be going up. That's pretty much an irreversible trend.
But I doubt that you'll see all that many of us "seasoned citizens" spending more time at York than we already do. Financial and health considerations would be chief among the reasons why, but there are other valid reasons as well. Truth is, I expect that many or most, after being retired for a while, will elect to make York a once-a-year trip.
Loads of truth here. I am semi-retired but still very active, and have cut back on attending the York event to once a year in October. My decision to cut back is not financial more than it is need. After 30 years of collecting and a layout nearing 85% completion it has become very obvious that I need less trains and train related stuff than when I was 30. We will continue to attend the fall meet for the chance to socialize with some of the best people in the world. While I may pick up perhaps $100-$150 worth of odds and ends, sharing the hobby with like minded people is always a joy. We also look forward to seeing friends from afar at fall York that we only get to see occasionally.
As for the bandit meets; I see these being good for those that want to stock up!