BTC for 2018. POW is quite strong at the moment, and its value its not high enough for any governments to plan to attack it.
If considering a long period of time, i would say new consensus mechanism is required. Right now i didn't see any projects that could possibly fight against btc, apart from the one i in

.
Yes, its Phoenixcoin. Soon after hard fork Phoenixcoin will better than bitcoin. I bought some coins and wait for hard fork and annonced mobile wallets in this year and after that I'm sure that the coin's price will soar like a phoenix.