Many cryptocoin have no real usevalue and by time these kind of coin will fade away
The price that the coin is attached to doesn't make the coin valuable. If the coin works then that is what will make it have value.
I quite agree with you, main cryptocurrencies will survive in the long term and the smaller, less established ones will crash and burn, due to a lack of interest or requirement for their purpose. This is because many of the almost-2000 coins on the market are very similar in the way that they work and they dont bring any new ideas, concepts, or services to an already full table. It is highly likely that any coins that dont have a unique selling point will become completely superfluous to requirements and will be ignored in favour of those offering something special.