I think that most promising alt coin right now is RIPPLE. The future of her seems very promising to me due to real life project assosicated with lots of BANKS, you can easily see the Banks which are interested in RIPPLE. I would not say, it is going to be like x10, no one tells you that. But it may be , perhaps even more. if you examine the Project, you will face low transection fees, and also it is really fast at transection.
Decision is yours, but I were you , I will definetly consider to buy some RIPPLE. 2018-2019 will be her.