Are you that sure about that number that you will have all the dangers of a hard fork with no replay protection when it is years, maybe even decades from potential necessity?
Yeah, this is real problem. Here i agree with you.
I can very well imagine that everyone might use one big Lightning Network in the future and that there will be no need of ever closing it. There is also a cost to closing a channel, so there is an incentive of not paying mining fees that people might not want to ever close it. And people might not worry about the benefits of closing a channel as much as you think, since the only benefit is that there is no risk of your funds being lost.
Lightning network was created mostly for small payments. For example you open channel with some product shop. Or with your friend. Of course, you're able to use others channels but in that case you must pay fee as you know (and also it is risky idea. hackers don't sleep). So someone will close 10 channels per year, another - noone. So i took average number.
It makes sense to assume that people will not open a channel with a friend, but with a big well known node that has open channels with many other users.
Lol, this is some kind of exisiting bank system. Trusted nodes == banks.