DJ_Tempest: I feel a little disappointed that we haven't received this update too. However, I have quite a bit of faith in GOG; perhaps it is an oversight. Might it be appropriate to file a ticket or shoot them a quick e-mail (or has someone already contacted staff regarding the update)?
I don't think GOG is responsible for putting out updates. Most likely it's entirely up to the devs if they update their game or not.
However, people are starting to realize that games on GOG aren't being updated in a timely manner. If games bought on GOG consistently get month-long delays between updates compared to other distribution platforms, customers might very well decide to start shopping elsewhere.
When getting a game that's available on both GOG and Steam, I've always gotten it on GOG. But if I'm going to have to get updates more than a month late by buying on GOG, I'm going to have to change priorities.
Basically, while I think the developers are to blame here (if they weren't willing to put out updates for GOG then they shouldn't have decided to distribute their game through it), I believe GOG's aloofness in this matter is going to cost them quite a few customers.