i am 100% sure that if someday bitcoin dies at least litecoin would not take its place, as you yourself said litecoin is just a copy with no useful feature. so i don't see any chance for it.
but other coins might have a better chance BUT i personally would not consider any substitute for crypto since if something huge like bitcoin dies other altcoins which are just small projects in comparison with bitcoin, would die too.
No because BTC and LTC given their identical nature, they can substiture eachother.
And so far I dont see any coin that come nearly close to their security. Maybe BYTECOIN can replace it.
Or if a more decentralized/anonymous approach is needed then Monero.
Other than that, these coins dont have as many devs, but who knows what the future holds right?