Sergey Lukyanenko is indeed creating a Fifth Night watch Novel, I know this due to my contact with "Seva" (My quote on Quote "Russian Friend") and apparently news about the creation of the fifth Night Watch Novel is reaching many Russian websites.
The plot, apparently consists of "Fighting the gloom" which, both I and him believe is rather stupid.
But still, The fifth Novel is in creation! Sadly for the rest of the world, we will have for a Official translation - Which could take many years to be released.
So, Go track down the websites which contain news upon the Fifth Night Watch book and turn on Google translate