Well, I am not sure why people keep saying that bitcoin will, may or could not achieve the scalability that is need in the current era. There are real world example of Visa companies and MasterCard as well who has more than 20k transaction per seconds capacity. If they can achieve it over the centralised server then why not we over the decentralised network where the blockchain runs through millions of personal computers around the globe! I guess it would be pretty easy to do if someone really puts their efforts into the blockchain and try to scale up the bitcoin nodes. Thoughts are welcome on this one.
The thing is that running 50,000TPS through a blockchain is technically possible, it's however not very healthy in a decentralized way. People quite often forget that every on-chain transaction needs to be validated and recorded in the blockchain that every node/computer has to save an exact copy of. In a decentralized network nodes aren't equal to each other and don't run on high end systems, this is a 'weakness' impossible to overcome.
The only way to scale beyond Visa & Co is to use second layers that aren't stressing the network and don't clutter the blockchain. Bitcoin's LN is already progressing and should be capable of processing millions of transactions per second. We still have to see how it works in reality and what its throughput is really capable of, but I'm very excited and confident. To add; Visa & Co use second and third layers as well, so we're definitely not unique in that aspect.