Each version of the Expo SDK has two parts – the JS and the native side. Their versions must match, so to use
email@example.com you’d also need the native client app that has the native code for SDK 23.
We haven’t released that client to the App Store and Google Play yet so you’d have to build it from the source on GitHub, which is probably a lot more work than you’d want just to try SDK 23. Plus you wouldn’t be able to use the Expo standalone app builders to create a standalone app with SDK 23 yet anyway.
We release a new SDK about each month (sometimes takes an extra week), so that updates come in a timely manner.