Most cryptocurrencies today are limited by their transaction volume capacity because every transaction needs to be distributed to every other node in the network - In other words, the Blockchain workload is serial (limited by processing speed not concurrency) and cannot be parallelized (distributed is not the same as parallelized). It's not possible to have a single blockchain handling more than a limited number of transactions/messages per second - This is a hard mathematical law, not a hardware resource limitation.
Sure, they can batch messages together to reduce transaction count (assuming they'd be willing to do that) but that only buys a bit of extra time. Looking at this I get the feeling that the Ethereum blockchain is doomed - It will be death by spam.