I think the most intensive development of cryptocurrencies will begin in 2020. This will be the development of a regulated industry and the replacement of Fiat money worldwide. I believe that.
The growth of crypto in the present is already intensive. Btc for instance, its price has reached very high today and less or no one expected it when btc just started years ago. And as for the question whether it is late to invest in crypto, it depends on the amount of money one can afford to lose. Also, crypto is very volatile and one could buy coins when the price is considerably low and profitable.