When would you think it will end, and what is the most promising coin as of the moment?
The first part is a very interesting question that I believe nobody has the definite answer. What we can see is based on the patterns of the price up to 2017, when the price tends to go up towards the end of the year, only to go down again afterward.
As for the second question, IMHO Bitcoin is still the most promising coin. The other coins (thousands in numbers) simply follow the price movement of Bitcoin.