Will Ripple face serious regulatory risks (as of 2018)?

There is one regulatory aspect, which can land Ripple in trouble: Issuance.

Ripple itself is not licensed as a money transmitter, and it would be classified as such if they sold XRPs directly. This is why the Coinbase deal is essential for Ripple, as Coinbase is licensed in every State in the US for money transmission, and hence can sell XRPs (on behalf of Ripple), without Ripple getting into trouble from the State regulators.

However, the US Regulators can go back in history and also on cases where Ripple has issued these tokens to American entities/individuals and look at this as a case, where money transmission laws were broken.

As of 2018, past issuance and any issuance done directly with US individuals/companies who are not licensed, could land them in a regulatory hot water.