Will KB Crossworlds be available as a physical DVD? I am no fan of Steam or other online content delivery site as I don't have an unlimited download quota like they do in America. (I live in Australia)
Not sure about Australia for the moment, but we are working on that.
Will it be widely available to buy, KB:AP was rare to get hold of as a physical copy.
THis will really depend on the territory.
Will the game have a restrictive and idiotic 3-online activations limit like the last KB:AP had?
I do not have information on that yet.
Is the new game an essential retread of the KB:AP story with additional quests, or does it remain unchanged but with the extra content separate like an add-on? (think Dragon Age: Darkspawn Chronicles)
Both - play AP with lot's of new stuff or play brand new campaigns. Plus FULL game editor to play with!
Will there be a KB 3 or is this the end? A parting gift, no more KB games...
Next game by Katauri will be announced sometime between now and November 
Will the addition of a full editor stop you from buying further KB games (if any) since you can make your own? I know I won't be using this editor at all nor play any mods as I feel only the original devs knows how to make a great game.
Will it come at the same time as the Russian version?
Yes it will come at the same time, Sept 17th.