For clarity, expiration date[0] is just means the JRE will not be considered "up-to-date" anymore. At that point, the JRE will check for updates and ask the user to upgrade.
We've using 8 in production for some time, as we slowly migrate things to it. We didn't want to start new projects without using Java 8 language features as it's such a dramatic change.
It has been feature frozen for a long time and even the pre-release builds have had a lot more testing and stabilisation than other software that people don't think twice about using.
There is of course a risk adopting new technology early, it depends what kind of things you are building/running.
How long till most people will target 8? I think we will wait for at least a few patches first.