Exactly what Title says... Will The 3DS Have The Only 2Mil+ Sellers In Japan (8th Generation)? 

Currently there are 5 games (MK7/NSMB2/PokemonXY/MH4/AC) that has hit over the mark.

Will there be any other titles? FF? SSB? KH3?

If you think it will name the platform and Game for it!

Also anymore 3DS titles will hit 2mil? 

Nahh, ps4 and some wiiU games such as Smash Bros and Mario Kart I can potentially see hitting 2+ million sales in Japan

FFXV should hopefully, VGC has 8 FF games over 2 mil. 13 only just missed out but PS4 is set to be bigger with the way WiiU and XBO are.
NSMBU is almost a given, already at 1mil now and has many years of great legs to come. Plus I feel like WiiU sales wont suffer as much in Japan as NA/EU.

Are we talking about handhelds and home consoles?

edit: I mean, I'll assume you are given KH3.  I think the 3DS will not be the only system with 2m+ sellers.  There's a lot of time for other systems to accomplish this too.

edit 2:  I don't have any specifics, but I think the PS Vita, Wii U, and PS4 all have a good chance at having a 2m+ seller in Japan given the right circumstances. 

Yeap i believe so too. What games is the question! 

next pokemon game?

Well, I suppose that Smash Bros and New Super Mario Bros U will do 2m in Japan for Wii U.  Kingdom Hearts 3, probably not.  None of the KH games were even close to 2m sold in Japan.  Final Fantasy has a chance.  There could very well be others, but right now it would be hard to say.

Maybe Final Fantasy XV. Maybe Mario Kart. Definitely NSMBU, at this rate.