Those are placeholders.
It will be more like X-COM than XCOM, but without typical economics (societies are in ruin, there is no cash). There will be also
- staff to manage buildings,
- limit of inhabitants
- and even artificial intelligence staff working for example in Medical Bay
This is only my speculations but probably you will need to dig out the rock and then build next structure for some resources also keeping watch for energy output, food production for each soldier and staff member etc.
And one of the downgrades from X-COM will be that bases will be randomly placed all over the world. Your task will be just to find them and expand when needed. You won’t select starting position and all the next bases positions.
Of course to compensate that there is a bonus, because those found bases will give you nice hint of game’s lore, research technology and progression in the campaign (this is my speculation based on rumors showing here and there).
EDIT: Nice addition will be turrets which will help defend bases during alien attacks. Or at least I hope they will add it.
Unfortunately it is planned. Well, quite many players look forward to this feature. Thankfully it will be incorporated in inventory system and by changing armor or mutation elements on the soldier we will also impact his stats.