Actually the original announcement was for DQXI and they said they were interested in bringing DQX to NX, then they quickly retracted all statements regarding anything NX. Now they are confirming DQX only, no re-confirmation of DQXI (I think it's set in stone but until we get the re-confirmation, anything goes).
That makes 4 officially confirmed games.
You can't say that Mario Kart is speculation IF Mario isn't. :P Mario Kart games more often than not outsell Mario games. MK is a guaranteed sales success.
AC will not go mobile only, from what they said of it so far, it sounds more like a companion app. Plus Nintendo's strategy is to convince mobile users to buy Nintendo systems. AC mobile will most likely be but a small taste of AC with micro transaction with the goal to get those gamers to buy an NX or 3DS and it's respective AC game. Heck ACNL is getting a major amiibo card integration update in the fall which is the same time AC mobile comes out. Coincidence? I think not. ;)
That game will be 4 years old come november (in Japan at least), I think it's a good indication that Nintendo will incorporate AC mobile and amiibo cards in AC NX.
Nintendo has to pay apple about a 30% cut of all sales of their upcoming mobile sales (No idea what cut Android gets, probably near the same amount). On the other hand, Nintendo gets 100% of the profits if people buy Nintendo games on Nintendo consoles.
Same goes for Fire Emblem, it sounds rather like a FE light version for mobile, trying to hook players into getting the future NX version (and 3DS games).