Anyone know what game studio/publisher owns the right for the games of defunct Troika Games?
This shortlived games studio release three CRPG's, each considered cult classics. Games were released horribly buggy but thanks to game's active fanbase each have fan patches developed for them that are still being updated.
Games by Troika Games:
Arcanum: Of Steamworks and Magick Obscura - [url=http://en.wikipedia.org/wiki/Arcanum:_Of_Steamworks_and_Magick_Obscura]Wiki[/url]
The Temple of Elemental Evil - [url=http://en.wikipedia.org/wiki/The_Temple_of_Elemental_Evil_(computer_game)]Wiki[/url]
Vampire: The Masquerade - Bloodlines - [url=http://en.wikipedia.org/wiki/Vampire:_The_Masquerade_-_Bloodlines]Wiki[/url]
Links to fan patches:
Unofficial Arcanum Patch () - [url=http://www.rpgcodex.net/phpBB/viewtopic.php?t=24419]Extra Pack - Arcanum 1024x768 Edition
ToEE Circle of Eight Mod Pack
Unofficial VtMB Patch - Forum

Vampire's easy. Activison was the publisher and White Wolf/CCP holds the rights to the original Vampire franchise. So Activision owns the publishing rights to the video game while White Wolf/CCP owns the copyright to the entire IP. If GOG were to try and get the game, they would probably need to work with Activision. Unfortunately, the game is still selling for $20 on Steam and Direct2Drive, so I doubt it will come here any time soon.

I bought Vampire Bloodlines the day it came out, it's awesome, but it's broken on a 64-bit system with at least 4 gigs of RAM.
If it somehow makes it to GOG and that bug gets fixed, I don't care how much it costs, I'm buying the game again.

It doesn't. It only uses the Source Engine, but doesn't go any further into Valve's "system" than that :)

I have the steam version, maybe that works on x64 systems

There is no difference between the Steam and retail box versions of the game, other than the DRM method. The problem isn't even really x64 or the amount of RAM. The retail box version does have an install problem with x64 systems, which the Steam version avoids, but there are fan-made patches that eliminate the problem with the retail box version as well. The 4GB+ RAM thing is actually a problem with Nvidia's drivers that causes them to see systems with more than 4GB of RAM as somehow having much less, which makes the driver automatically tone down the texture rendering, leaving the game looking "muddy". That can be avoided by using MSConfig to temporarily set your system RAM to something less than 4GB (at least until Nvidia fixes their drivers).

We'll never see it again, ever.

Here is a link with info and tools for easily installing
Bloodlines on x64 with 4GB or more RAM.