What do you mean, whats going to happen in 10-15 years?
Do you think autism is a new problem and there aren't currently adults with autism now? Same with ADHD etc? My brother had ADHD as a child, he's now 30, he was able to come off medication in his early 20s and is better placed to deal with difficulties as he's now an adult.
Even NT kids have tantrums sometimes - the world is overwhelming to all kids, but far more so for some. Are you worried about those NT kids lying down in supermarket aisles as grown adults and kicking off?
Many people with ASD learn to adapt as they mature and become more experienced in the way the world works. It won't go away, but it's certainly easier for an adult to manage these issues than it is for a confused child.
Your comments are downright bizarre and show a complete ignorance of the realities of the situation.
OP - once I was in M&S with my twins in a double buggy, one of them reached out and grabbed a display stand and I didn't see it, so of course the whole thing was toppled as I moved away. The staff were incredibly kind, insisting I didn't need to pick it all up and these things happen (I'm disabled myself and taking them out is really difficult for me so this really got to me). If I'd been treated this way I'd be scared to take them anywhere, it's really not on.
I would go straight to head office now - they've had plenty of time to handle your complaint.