They said in one of the recent live shows (during the 2.2 update I think) that space legs are definitely in the pipeline, just with no ETA and that they are still trying to decide what we could actually do to keep it interesting once we have them. Personally I'd expect them to be the central theme for a Season, not a point release update so I don't expect to see them any time soon.
Players that have clipped through walls etc (mainly in VR) have said that the graphics are partially in place behind doors etc, so they are clearly working towards it already. If they were not, there would be absolutely no point in creating the interior detail past a fixed bulkhead