Dash is primed for mass scaling. The masternodes keep infrastructure running well, and the onchain scaling approach means there isn't really a realistic limit.
We worked with Arizona State University's blockchain research lab on scaling research many years ago, check it out:
https://dev-wpc-blockchain.ws.asu.edu/block-propagation-applied-to-nakamoto-networks
Beautiful, I read the summarized report and what is suggested for block size through the simulations seems a much better scalability approach.