I think there should be much care towards avoiding proof of stake. It is antithetical to the design of true cryptocurrencies and is centralized by design. Any proof of stake could be considered a pyramid scheme to a degree. Proof of Work, albeit now aging, is a great tool for distributing coins to new users and anchoring the coins to real life value. I think the real future of crypto lies in Proof of Service which is the model Dash has lead in.
In depth differences can be found via a quick search for: proof of stake vs "proof of service"
As the masternodes in Dash evolve, they might be rewarded on their effectiveness on the network. The PoW component will remain for security, but I think it should move towards avoiding asics, in similar ways to monero, and optimize for cpu. Monero has made hobby mining profitable again, although providing meager returns. If mining is built to be more distributed, it provides more resistance to centralization (and 51% attacks) and lowers the barrier to entry for those who might not be able to access dash through an exchange. The other possibility to reduce barriers is to enable trustless shared masternodes. This would have to be supported by a third party service, but would increase the size of the masternode network and allow dash users to grow their wealth if they do not plan on using it, thus increasing it's strength as a store of value.