Could be. I think paid email is becoming slightly more popular with this recent economic downturn. I think my concern is how do we balance cost with spam prevention. Paying for infrastructure is important, and relay providers should be able to be compensated for their services, but I think my social interaction would be limited if I always had to think about money when chatting with people. I'd be way too concerned with how much I'm spending just to share my thoughts, make frens and build a network. I'd probably just stop using social media altogether. 

Do we just go back to cellphone minutes? 
How much does unlimited minutes cost?
Does an upfront cost model work. 

Sure operators can play with these models, but in the long term they will need to settle on some payment model that works. 

And finally I think lightning, at the moment, is just a bit too complicated for a non insignificant portion of the target nostr audience