I think we can count on that (barring extraordonary circumstances like a meteor hitting the main Mongoose offices).
After all, how could they do EA and Minbari, while leaving out the Centauri and narn... and once they do the big four, I expect them to turn their eye towards the League, the minor powers and the Ancients...
I'm sure they won't run out of stuff to write about for a looong time! :wink:
The reason that there hjasn't been any official word yet is that Mongoose haven't confirmed their 1 half 2004 release list. But I'm sure that the Narn book, along with the two Season books will be on there.