"expansion announcement" - not that expansion will come the next day or any time soon...
At current updates rate, we will have at least 1.5 before Christmas. So there is a lot of time to make additions to the game. Plus, there are a couple of posts on the forum about "expansion team is separate from core dev team".
as to "why?" and "what for?" questions:
https://www.youtube.com/watch?v=8yd-m9AR7mY
Totally forgot about PAX Prime. It make sense to separate 1.4 and expansion news for two shows.
Yep... I understand that... But the question still stands. Let's assume this is an announcement for the release you're talking about, to get up and walk around ships and stations, and it will be available say early 2016.
1) The question still stands... You get out of your seat in your ship, look down the interior... and do what? ™ Tell me some things that you'd do that will add to the gameplay and not prove a five minute wonder?
2) Now assuming you've come up with some interesting ideas of what you will do when you get out of that seat, consider in the past 6-12 months, how much the core gameplay has moved on. Consider how most (if not all) of it is simplistic self contained mini-games with none of them actually affecting each other or giving rise to any emergent gameplay. Consider how probably the things you're suggesting are in a different league to what we have in ED (which have had years of development)...
Now, I'm in no way suggesting ED couldn't have a DLC to add the ability for players to wonder around their ships and stations. That's the easy part. The tricky bit is giving them anything of interest/worth to do. And to achieve that would mean giving a level of game mechanics and depth not even witnessed in the core game yet, yet alone a DLC for it.
I'm not trying to be glass half empty here. Just pragmatic and realistic. If we want to get out of the seat of our space ships we need entertaining, engrossing and intelligent activities to do supported by impressive gameplay mechanics. And I'm not sure we even have those yet
in the seat.