There is definitely a touch of the feeling from Pratchett's later DW books in the Watch Trilogy. The same kind of, OK there's Trolls, Dwarfs, and Gnomes, but with vampires, werewolves, and most background characters generally being nasty minded people who would sell their own granny for a dollar, (or at least rent her for a few hours), there's none of the fairytale "We must defeat the evil king and save the little elves" vibe that accompanies a lot of fantasy novels, (not a bad thing of course, mostly). Which is a similar feeling I got from Lukyanenko's books, which I think is born in part from the fact that these are Russian stories, set in Russia with no consideration for western audiences, (Definitely a good thing) as well as the deviation from the usual swords and sorcery.
Regarding the 3rd film. I'd read that the chances of it are quite slim. Apparently Timur Bekmambetov was all set to make all three films. The studio however has other ideas. Basically, the film Wanted, (James McAvoy, Angelina Jolie), is actually what should have been The Twilight Watch. Indeed Bekmambetov describes it as an American version of The Watch. I wouldn't hold your breath for The Twilight Watch. Not from the same director anyway.
It seems that beggars can actually be choosers.