FWIW, we're currently talking to both Sony and Unity and we're all working hard to to optimize performance of Firewatch on PS4.
It's tricky, because it really requires all three partners working together to improve — it's not something we can tackle on our own, unlike a game bug — but we'll definitely continue to patch all platforms with every content and performance fix we can over time!
To summarize: we're on it. :)
(I've played through the game multiple times on a PlayStation 4 and enjoyed it thoroughly! But I'm not a PC gamer so…)