It depends on how big investors and people in general adopt cryptos during this year. Total market cap of cryptos, after surviving recent FUDs and SEC being more pro cryptos, could reach historic values. We don't have to think as individual coins or tokens, but as adoption of blockchain technology. If that happens on a wide scale during 2018, the big ones (btc, eth, etc) will also reach values that we haven't seen before, and there's always the possibility that btc could lose its king position, and eth could take that place. 5k seems like very probable, but predictions are usually very inaccurate in this market.