Factions. Intra-politics is, in my humble opinion, the main difference between 4X games and grand strategy games, and this will deliver.
Traditions. The best feature of civ 5 getting carried on by Paradox fills me with joy. My only fear is that there wont be enough traditions for the late game, but alas, that's what mods and further patches / expansions are for.
Habitats, ascensions, galactic wonders and generally talking, tall gameplay. Now this fits my gameplay style much more than map painting could ever do!
Living standards. As minor as it might sound, I really think that this simple change can add a lot of strategic depth and more important, flavour to empires. Is your empire a nice place to live or not? Is it depending on which species you are, or which sector you inhabit? Sounds like cool decisions to make.
Generally talking, it would seem to me that while there are some things that will still need development (warfare, diplomacy, hiveminds, civics), there has been a conscious effort at trying to improve the flavour of the game, and most importantly, the flavour of what I think that is its core, the ethos axis. This is my most wanted "feature", even if it is not something distinctly defined content.