In the average preview cycle for most linear/narrative-driven games, we are shown between a third and a half of the 'PvE' content, or, perhaps more accurately, levels or missions that take place that far into the game. Closer to launch, the dev shows all the competitive multiplayer content. So it's not entirely surprising that we've seen most of Old Russia and a snatch of the Moon so far, as that's comprising approximately a third (given how little time we had with the Moon, we could hardly see it in detail) of the physical space of Destiny's PvE. I'm sure we'll get more Crucible maps, and gameplay from them, at PAX, whenever that is, and that'll likely be our lot before launch.