I suspect Litecoin will fade into non-existence, with Peercoin (or some other somewhat novel approach to the problem) replacing it. LTC has nothing over Bitcoin...it's merely still mine-able on GPUs, which is good for miners that have GPU farms[1], but not all that useful for anybody else. Maybe it has value as an alternative blockchain to BTC, should something terrible happen to BTC, but many cryptocurrencies could provide that.

Doge is roughly identical to Litecoin, but more fun.

1-I have a modest GPU mining setup, and I mine LTC and Doge.