I will have to go back and double check, but I believe it's a case where the kickstarter backers get content included with their base game (at no extra cost) that people who buy it now won't, but after a period of time that content will be released as an expansion for everyone.
edit: looking at the campaign there are some things that are kickstarter exclusive, but in the grand scheme of things it's very little content.
looks like it is like 6 cards and some nicer dividers for the cards, in a game that comes with over 300 cards.
the rest of the promo stuff will likely be released as an expansion later. (in fact opening up my game box if you want to know the name of that likely expansion I can since they are nice and include boxes for the expansions that are included via kickstarter pledges lol)
that being said, while I know it sucks to have some content you don't have, at the same time, in a game with a ton of content like aeon's end it doesn't matter to much
.
is what should be in the game in general.