What happens when you run out of cloud storage for Lightroom CC?

Currently I am using the Lightroom CC with 20 gigabytes. I'm still within that range because I've been culling my photos before I upload them to lightroom. My question is, though, what happens when you run out of cloud storage? Can you continue to use lightroom locally and upload photos/edit them just without the cloud functionality? If this is the case I would switch to uploading all my photos to lighroom and then culling them there. Or will it make me buy more storage? 

Any help would be appreciated.