I think you're making a lot of assumptions about what LN is capable of, and what it requires in layer 1 blockspace to do it. It will get more efficient over time, and if it does start to reach capacity there will be new solutions thought of to deal with it.
Or maybe there will be a more valuable use of blockspace than opening and closing channels and LN will die. Either way the market will figure it out, I wouldn't worry about it.