The only potential downside to the announcement is that iOS 12.1 hasn't officially been released yet. But the upside is that if you're willing to join Apple's public beta program, you're only a few minutes away from sending a frozen face emoji.
To sign up for the beta program, visit this website and follow the instructions. The process includes installing the beta profile on your iPhone ($1,000 at Amazon), restarting your phone and then downloading the update just like you would any other OS update. It's easiest if you visit the beta program website on the iOS device you're going to enroll.
However, it's important to note that the update is in beta, meaning it's likely there will be issues and bugs. It's a good idea tobefore installing the beta.
Of course, the other option is to wait a few weeks and let Apple release the official version.