The main R connection to both platforms — from the main floor of the Oculus — is open now, of course. I assume you're asking about the other two, which connect directly to the downtown platform. There's one at the Oculus balcony level (just above it, actually) and one in the 4WTC retail lobby. I don't know when those will open. I haven't seen any work being done on several recent trips through. There's not much space — if any — to finish, so it might be an issue of turnstile availability.
The new passage to the E still needs some work. I'm not sure when that will open, either.