Yeah seems like it will be a good side, but early days so who knows they could announce something to change our mind!

obviously assuming the game goes well after release. Not a given it will happen, but that is the objective, we can only wait and see how well it goes with the 4 launch races.

I think they're going to add more factions and subfactions in the future but for classes I dont know (maybe more specific classes)

so at the end we may have all the factions (except sisters of battle and imperial guard) and 2 or 3 more chapters

Said it before and I say it again. If anything, it's for the best that they dont go too far with the different classes and factions to begin with. Focus on gameplay, balance, immersion. If it's all working - add more.

All races/factions will be in the game in one war or another if it's successful enough, which I do think and hope it will be. They're keeping it simple with 4 in the beginnig, which is a very good decision imho. I hope that the next faction to be included post-release is IG, I have a feeling they will be very fun to play as.

Even if the other factions are released as DLC for credit crunching prices... I will still get them I am waiting for the Necrons to come into play and see how they will work within the game!