Don't Wait If You Want Face ID
If you want Face ID on your next iPad, you shouldn't wait for this version of the iPad.
The 2018 iPad Pros are the first iPads to go with Face ID over Touch ID. Instead of using your fingerprints to unlock an iPad Pro, you can use your face.
Face ID is also available on Apple's newest iPhones.
Unfortunately, it looks like the 2019 iPad will skip Face ID AND stick with Touch ID. This doesn't come as much of a surprise given the device's price point.
If you want to unlock your next iPad with your face, you'll probably have to go with a iPad Pro.