Scalability has always been an issue for crypto. Because of the 1mb block size of the Bitcoin network, it can only facilitate up to 7 transaction per second. Other cryptos have made improvements, yet when compared to VISA's capability to handle 24,000 transactions per second, the improvements seem trivial and inadequate.
Lightening Network could be a solution, yet may ruin the integrity of the original blockchain.
Will DAG based technology like IOTA and Paymon replace blockchain because of much higher potential for scalability? We shall see in coming 1-2 years.