It has been in beta for a few months now and they just announced it officially today, I got it through an email:
Introducing Live View
This is our No.1 most requested feature and it starts rolling out today.
Those of you with current Ring Video Doorbells that have connected
them to the wires will be able to access Live View starting
today. Live View will also be available on Ring Pro.
Battery powered Ring will have Live View enabled in the next 1-2 months.
They also announced the Ring Video Doorbell Pro, see this thread for more info: