We are certainly seeing a significant bull run for Bitcoin, as well as for a number of other cryptocurrencies, and I certainly don't think it's over yet. While I'm not confident that Bitcoin will reach it's December 2017 high of ~$20,000 this time around, I am confident that it will rise much higher from it's current level before there will be any major downturn.

Having said that, I think "THE" coin to watch right now is Ripple (XRP). Of all the coins available today, I think that Ripple (XRP) has the greatest potential for very significant gains over the next few months. Currently trading at just over $0.30, I can easily see a 2x to 3x increase well within striking distance.