Hello, I wonder, can we still play the next expansion box (multiplayer) as we did before, 1 - 1? Or is it only for multiplayer-purposes? I hope not....

The box comes with rules for 2v2 games (which are already posted online), two challenge decks for use in 1v2 or 1v3 games only, and 6 objective sets (one for each affiliation) which can be used in 1v1 games but are all more useful in 2v2. If you never plan on playing multiplayer, you could probably get away with skipping it, but you would be missing out on a couple of objective sets that you might have wanted for 1v1 games.

ok, thx! the heroes and legends decks are again for 1v1?

yes