I didn't do the gap year thing or any travel in my twenties - just the way things worked out. Was fortunate though to visit European cities in my teens for short breaks, and then again in my thirties.
I've wanted to go to India for a long, long time and hope to some day spend a few months there, doing lots of yoga. Maybe I will be able to do this in my forties.
Would also like to see South East Asia. And Machu Picchu would be amazing.
Where have you been, and where do you want to go in future? Are the destinations you want to see doable in a couple of weeks, or do you want to go for a couple of months some day?
And finally, will long haul travel still be available over the next decade or twenty years, or will it get very expensive?