If that is true and they are going to make new content for the Attila Total War then probably it would be most favorable if they will make Caucasian DLC including Kartli, Armenia, Lazica etc.
Warhammer fantasy is not the thing they thought to catch attention. Before starting the new historical Total War title they need to keep historical-game-fans busy to experience themselves
with more fresh campaigns.
I remember your point about Slav DLC, you wrote that victory condition that was based on the religious, cultural, or social achievements but not only about the conquests are future of historical Total War games, and I fully agree with you. Even though, you know my opinion that Slavic factions such as Venedians or Sclavenians and even Anteans were not so important in 4th and 5th centuries as other
unplayable factions. Innovations such as new victory conditions for the each factions based on cultural and social achievements must be some kind of prerequisite for the future historical Total War titles.
They also could serve as kind of warm up for the next historical title, which as I think will be Medieval III Total War. But, still until they announce Medieval III Total War one more year will pass. Hence It is better to devote all their effort to improve Attila Total War, which is the most "realistic" historical title in Total War games.
I would suggest Caucasian DLC with new victory conditions based on survival and cultural achievements. That would make sense, it is easy to do DLC/FLC (3+1 factions that are similar with much alike culture and units), but with much different victory conditions that will make them to look unique.
Consequently, the information that you gave us from the forum is very promising, especially, for those of us who are waiting for Caucasian factions in order to fill the gap that Attila Total War has in this region. The most anticipated for me is to play with Kartli. I also wish that 395 invasion of Huns in the East (from 395 to 398) will be properly depicted in Attila Total War. It is historical game and the most important faction Huns are targeting the Ukrainian and Russian steppes instead to invade in Caucasia, Armenia, Cappadocia, Syria and Mesopotamia which they really did in 395. This was the first major appearance of the Huns in the global political arena against Eastern Roman Empire, Sassanids and their vassals/allies. So, the new Caucasian DLC with proper depiction of the Hunnic invasion in 395
will blow new soul to the Attila Total War. At least this will make the game to look more historical from the beginning and it will work for survival victory condition for Caucasian factions. Why I speak about
survival, because as we know from source and secondary literature Armenia was conquered by Sassanids in 428; Arran was conquered in 463, but was liberated in 482 and conquered again in 510; Kartli lost its Independence in 550s; Lazica was always under treat from Byzantines, Persians and Northern tribes but survived. Why so much, because all those kingdoms constantly under the treat of Byzantine Empire, Sassanian Persia, Huns, Alans (dozens of battles are depicted between Kingdom of Kartli and Alans in the 5th century, especially, during the rule of Vakhtang I Gorgasali) etc. Hence all this could be somehow included in the game.