The preview states the following:
In addition to its challenging new scenario and the Palantír, Assault on Osgiliath introduces a new Ranger hero, and a number of cards that support the Gondor and Outlands traits. You’ll also find cards that promote the construction of mono-sphere decks and that represent the effective traps, ambushes, and skirmishes that Ithilien’s scouts andRangers use to weaken their foes. Altogether, it’s a wide array of cards to support multiple new strategies, and you’ll need everything you can find to confront the Orc and Southron hordes and reclaim the city.
So we've got the Palantír and eight more player cards (not counting the hero). In those eight cards we're to see support for both Gondor and Outlands, support for mono-sphere decks, support for traps? Even a single more Outlands ally will be enough to strengthen the faction yet some more (especially if not of the Leadership sphere). I hope to see yet another trap surely but perhaps even better a card that fishes it out from the deck, though it is more likely we will see the already spoilt Anborn that brings a trap back from the discard pile. More than the above, I'm really hoping for a strong Gondor card, and by that I mean a card that strengthens a strictly thematic Gondor deck. Like: if all your heroes have the printed (!) Gondor trait, you... eh... win the game? No, not quite like that, but a decent ability to be sure.
And above all, I'm looking forward to see a strong Faramir hero card. We've been getting many articles lately, though more often dealing with the future saga or errata, could it be we see Faramir previewed today? Amon Din was out at the very beginning of July, I'm thinking Osgiliath cannot be far off...