It takes place in the Helius Cluster
Awestruck confusion: Toto we're not in the Milky Way anymore.
The survey indicates that game will take place in a cluster of hundreds of solar systems, well beyond humanity's usual territory. It's the cosmic Wild West, filled with "cut-throat outlaws and warring alien races".
We're also "far removed by time and space" from Commander Shepard's actions - presumably meaning this game takes place before you destroyed/integrated/did bad Illusive Man things to the universe (or so far after them that no one ever mentions them anymore because it's all a bit old hat).
You play as a "Pathfinder"
Your character's on a mission to find new, habitable planets for humans to colonise - think of it as pitched somewhere between Mass Effect's militaristic core (you're still shooting nasty old aliens) and Star Trek's peaceful mantra (you're ultimately not looking for trouble).
You'll be actively establishing settlements - which can be used differently, including Recon Settlements that clear map-fog and Mining Settlements that up your crafting materials periodically. Crafting extends both to your vehicles and your crew's equipment.
Speaking of crew, the survey indicates that there are seven party characters to recruit, including a Krogan called Drack and Cora, a biotic defender of some kind. They'll have the usual set of loyalty missions (which now open new skill trees as a reward) and uneasy relationships to contend with.
There's still a long-lost terror of some kind
Your travels will lead you to finding evidence of The Remnant, (and stop me if you've heard this before) an alien race as mysterious as they are dead, whose technology is the key to gaining a foothold in the Helius Cluster. You'll be drawn into deadly competition with at least one other faction trying to get their hands/paws/psychic tendrils on the goods.
Strike Team missions sound familiar, yet interesting
If you've played Dragon Age: Inquisition, you'll remember the War Table. A sort of ambient mission pseudogame, it played out mini-stories across Thedas in real time, netting you little rewards as it went. Mass Effect 4's Strike Team missions sound much the same, as you send bands of mercenaries across the cluster to collect resources or explore in randomly-generated missions.
More interestingly, you can choose to take on Strike Team missions yourself, using a separate set of multiplayer-only characters, all of which plays out in what sounds like an updated version of ME3's sorely underrated Horde mode multiplayer. You can do this alone, or recruit friends to fill in the ranks, earning themselves rewards for their own multiplayer games in the process. It sounds as though Horde mode will be its own, entirely separate, multiplayer component too.
There are lots of little touches
Mass Effect's always had its fair share of peccadilloes, but it sounds like some of the old favourites are being smoothed out. We already knew that the world's bounciest Jeep, the Mako would be making a return for planetary exploration, but the survey indicates that transitions between space exploration and planet-surface fun will be seamless, with none of the loading screens or generalised faff of previous entries.
Dialogue's at the heart of Mass Effect's experience, and the new game seems to be taking that more seriously than ever. We're sure the stilted good-bad-neutral choices will remain, but more opportunities to interrupt or take action (such as pulling a piece to intimidate someone) mean it should stray a little closer to realism.
The game seems to be nabbing from some fairly high-profile sources to fill itself out, too. Khet Outpost raids have you ousting outlaws and conquering territory - hello, Far Cry - while Remnant Vault Raids couldn't sound more like Destiny's premier mission attraction, with all the difficulty and huge rewards you'd expect.