This development could mean any number of things for the future of cryptocurrency. The situation is very fluid, and market valuations are both constantly calibrating and volatile. Its going to be difficult to get a clear picture until Bitcoin Cash has been running for a little while (or fails), and until Bitcoin implements its segregated witness technology later this month, and then doubles the size of its blocks three months later.
Improving cryptocurrency as a transaction medium will depend on maintaining the high level of security that Bitcoin has always ensured, while also improving transaction speeds. Bitcoin will continue to be highly secure, but how much its transaction speeds will improve is unclear. Bitcoin Cash, once its difficulty has adjusted, could have transactions processing in two minutes and 30 seconds. The security of the Bitcoin Cash blockchain, though, is unclear.
It will also depend on miners and users vision for the currency. If Bitcoin really does undermine the decentralized nature of the network, and the democratic possibilities of the blockchain technology, people may look elsewhere for a cryptocurrency with more exciting potential.