If what I read on the Summer's Gone Season 2 Steam page is to be believed, it'll be a massive update, it states that once it goes live in early access, it'll already have Chapters 1-4 (of season 2 obviously) included, which will contain around 12,500 renders. He plans to then release Chapters 5-11 over the following 3-4 years which will then conclude season 2, which will add an additional 20,000-30,000 renders when done. I presume this means the total for all of season 2's 11 Chapters would be 32,500-42,500 approx.
If you'd like to read this for yourself, check out the season 2 Steam page and it's under the Early Access bit once you scroll down a little.