I think
Ethel will remain a dusty relic that will perhaps occasionally be chosen by edgy parents, but won't get truly popular. Although, I never would have though people would like
Edith again and I was quite wrong about that! I suspect that
Edith got a boost from Downton
Abbey, so maybe if we have an interesting
Ethel enter pop culture,
Ethel will get the
Edith treatment.
I personally like
Ethel and would use it, and my partner thinks it's a gorgeous name, but that's because it wasn't common in their culture so they'd never heard it before I introduced it to them. They don't have the same "old lady" associations that others do. I do think
Ethel has a lot of cultural baggage that people will either love or hate.