I don't think any Netrunner product has ever had a release date more specific than Q4 2017.
It's widely said that entire cycles are printed and shipped to Minnesota at once, which is why we see delays between cycles rather than in the middle of them. If true, then the upcoming statuses for all data packs that aren't the first in a cycle are lies.
We do know that cycles are designed all at once, so no, it's not likely that Down The White Nile is actually still in development.
I'm hopeful that we'll see the Revised Core before Christmas, but at this point I don't expect to see any of Kitara until the new year.
ETA: Also, the release date given in the announcement for Down The White Nile is Q1 2018, so they aren't actually late yet. Unless they've edited the article or something.
Also also, I'm kind of surprised to hear that X-Wing gets release dates in advance. I thought this problem was FFG-wide. For Netrunner, it used to be even worse: stores were allowed to sell packs whenever they arrived, rather than having to wait for a specified release date, so there weren't release dates even for products that had actually been released.