Read the letter for myself (I encourage you all to do the same, don't rely on heresay or even CDPR's own words) and I'm kind of shocked.
Most of the letter is fine, but the last few paragraphs read a lot like extortion.
"Both we and you are, after all, fully aware of the fact that even going public with a copyright claim may negatively impact the Group’s reputation and further growth
This is particularly true if the claim concerns your core activity and your most important product... We can reasonably expect that the negative consequences of the fact that Mr. Sapkowski has not received his due compensation, and furthermore,
that the validity of your copyright contracts has been called into question, may translate into a decrease in stock prices significant enough to exceed the demands formulated in this notice."
Sapkowski could be legally in the right here, despite CDPR's claims, if certain Polish laws hold up. Apparently, and this actually is heresay on my part, there's some law that allows Polish creators to reap additional rewards from unexpected successes, even if they initially agreed to a lump sum.
Whether he is morally in the right is another subject entirely. If CDPR decides to fight this, which it sounds like they will, I fully expect them to pull quotes from interviews conducted with the man in the past, where he admits it was stupid of him not to take a percentage, and that he dislikes video games, etc., to try to harm his character. Note, I'm not saying CDPR themselves would be "bad" people about it, but lawyers are lawyers.
My personal opinion? I think Sapkowski deserves absolutely nothing. I don't think it's a stretch to say that The Witcher 3 (and 2)'s success is the sole reason he now has a Netflix series in the works, and his books are now translated for English-speaking western audiences.
That wasn't his work. It was CDPR's. He didn't lift a finger. Apparently, he didn't even consult with them the way Mike Pondsmith has been with 2077. By the way, can we take a second to appreciate how awesome Mike has been about everything? That's a guy with integrity, one you know won't come back to bite you in the arse 10 years down the line.