I believe BTC is here to stay, due to it being some form of "backing" currency for all other crypto currencies. I guess one could claim the same for ETH, since it's used for many ICOs.
But apart from that I am not sure what the future of ETH or LTC will be. To me it seems some adaptations of ETH have a much clearer use-case and therefore are likely to raise a lot in value in the future. One of the ETH based coins that I really believe in is OmiseGo[0] (OMG) which will bring banking capabilities to many people that currently don't have a bank account.
