Dropbox changing certificates to more than two?

Thanks for the post! It sounds like you're referring to this earlier thread.

Our current certificates will be expiring, so we'll need to update them before they do, and we're also planning to move away from using EV certificates, which involves using a different root.  In order to handle that without disruption, we recommend trusting both roots.

I don't have any other information to share right now about if/when we may be expanding that further, but this is open with the team to formalize this to give more specific guidance in the future.