Sorry if I'm misunderstanding the situation, but does your friend have the base game (ARR) on PC yet? If so, he should be able to log in on PC and play up until he reaches the HW wall. Alternatively, he could play on PS4 beyond that until launch day and then switch over to PC. My understanding is that ShB does not include the base game, only the HW and SB expansions, so the base game needs to be purchased again for PC. If I'm wrong about that, someone please correct me.

As for early access, I have no idea if HW and SB will become accessible at that point for those who don't have them yet but have a pre-order of ShB. I would hope so, but that's something we won't find out until the time comes (unless a mod wants to step in with a response).