This isn't an April Fool's joke at all - 2K Marin itself states they are true.
To anyone who seems to be a bit doubtful, I'll clear up a few things:
1) The stuff we see in the magazine isa PREVIEW: that's to say there will be a lot of new stuff which they don't want to reveal now. That means new plasmids, new weapons (it won't just be the drill and the rivet gun - trust me), and new environments.
2) There is multiplayer. I repeat, there is multiplayer.
3) There are outdoor underwater levels on the sea bed, which has been utterly confirmed. Underwater combat is going to be awesome.
4) There will be new enemies - I can vouch for that. I think there will be massively mutated splicers, new types of Big Daddy not to mention the infamous Big Sister.
5) If you're annoyed that you wanted to see Rapture BEFORE the civil war, remember that there will be Bioshock 3 and possibly even Bioshock 5 and 6. There will be time to explore that - and anyway, it's supposed to be a "sequel and a prequel" so I'm guessing you will.
6) Think playing as a Big Daddy might get boring? Not really, if you think about it the 1st Big Daddy should be unique to the rest, maybe even more human than the rest.
My main point here is the stuff in this article isn't the only new content in the game - I think it's only scraping the tip of the iceberg.
this could be cool but dang i was hopeing for a prequel so i could witness the fall of rapture oh well it sounds like a pretty good concept but just protecting little sisters the whole time yes will get very boreing