I hope WD keeps holding that stance. Criminals should never be rewarded for their dirty 'work'. If they end up paying even a low number of coins, it will only incentivize these bastards to continue doing this. Eventually it won't have that much of a real effect, since the number of people watching it through illegal streaming/download sites are lower in number than those who are willing to pay for content. Another thing might be that they will sue every IP address that is seeding/sharing this not yet released content. People are more cautious about everything related to pirate content.
I have to agree, paying them gives WD no assurance that the movies won't be released. If I were the hacker and received the coins, i'd auction the movie off, or sold it on one of the TOR marketplaces to earn twice. You can't expect a thief to have honor.
IPs are not that easy to trace, there are programs that block the sharing and not allow anyone to download from you when you're using torrents, so when you download, you're not breaking any laws. You're taking from the Internet something that is given for free and don't participate in the sharing process. As for the hackers, i'm sure they are behind multiple layers of protection.