I just want to show how likely/unlikely this is. 

In order for the PS4 to outsell the Wii U in Japan by say January 2016 it must close a gap of 1,154,105 in Japan (from Feb 1 2015.) That means it must outsell the Wii U by 24,403 on an average week. If you meant some time in the first half of 2016, such as, say, June at the latest. That would imply an average of 15,516 more sales than Wii U on a weekly basis. 

Currently the PS4 averages around 21k per week and the Wii U 19.5k per week. 

Do you predict Wii U sales in Japan to decline and PS4 sales to increase so much that the gap per week is about 20k on average, whereas now it is about 2k. That would mean that either PS4 sales will have to double and the Wii U remains the same (on average,) Wii U's sales decrease by 50% and the PS4's sales increase by 50% or some combination in between these cases. I'm sure FFXV will increase PS4 sales considerably, but will they increase the sales so much that the PS4's sales double or even become 50% more than last year's? 

Final Fantasy XIII sold 1.87 Mil  in Japan, and 1.5 MIl in its first year. Let's assume FFXV sells similarly, and let's also say that for every five people who buy FFXV one doesn't have a PS4 already, in anticipation for the game. 1.5 Mil/5 = 300k extra hardware sales. The PS4 sold 992,112 last year. And that is including its launch, but excluding the month of January and half of Febuary. That would be about 30% more PS4's than 2014. That would also mean, only an average of 26.9 k PS4's per week. So in order to sell the 24k more than the Wii U that it needs to outsell it by January, the Wii U needs to average about 2k Japanese sales per week for the rest of 2015.

Sure the PS4 has other games coming, but a lot of their audiences overlap so we have no idea how much of system sellers they will be. 

2016 seems way to early for the PS4 to outsell the Wii U, unless it starts selling like 40k/weekly in Japan, on average. That is around what the PS3 was selling in its peak. So if you think the PS4 will outsell the Wii U by early 2016, but won't outsell the PS3 that is kind of a conflicting set of predictions, in my opinion. 

Monster hunter 3rd portable does 500k in a 10 millions userbase wii u will never have 10 millions userbase.

People buy a wii u for Nintendo first party game only while wii was bought by people who want Nintendo first party game too and casuals gamers and both lack hardcore games.PS3 and PS4 in other hand was always bought for hardcore 3rd party games.

So if ps3 software sold more then wii,ps4 will sold more software then wii u.

With a very good possability of Final Fantasy, Dragon Quest, Kingdom Hearts, Monster Hunter, and Persona all having mainline games exclusive to PS4, it will easily outsell WiiU. With that line-up plus so much more, it should also blow buy PS3 quite easily. My guess would be PS4 overtakes WiiU early 2016.

With Remote Play set to come to nearly all smartphones, and a Sony brining their focus almost 100% on PlayStation, I expect PS4 to sell quite better than people are expecting, even in Japan.

Japan seemed to be the only region the Wii U was doing OK but lately it looks like PS4 will eventually overtake it by maybe mid summer.

What wii u doing ok in Japan how that?It's the place where it sold the less

It will take some time, but the PS4 will outsell the Wii U. It does have the games, that we know of, to give it a boost. More games like Dragon Quest can definitely help.

I'm going bold and say ps4 and that good jrpgs are going to flourish.

3DS?

The only ones confirmed are FInal Fantasy, Persona and Kingdom Hearts. Dragon Quest has just as good a chance of releasing on the Wii U as the PS4, both of which are slim chances considering the history of the series releasing on popular Japanese platforms. Persona 5 is a PS3/PS4 multiplat. There is nothing to indicate that Monster Hunter will come to the PS4. 

Japanese sales for the announced PS4 games predecessors:

FInal Fantasy XIII - 1.8 mil

Kingdom Hearts II -  1.38 mil (but last new console release was ten years ago.) The series has declined on handhelds.

Persona 4 -360k

Japanese sales for top 5 Wii U games in Japan:

New Super Mario Bros U. - 1.23 mil

Mario Kart 8 - 900k

Wii Party U - 810k

Super Mario 3d World - 630k

Super Smash Bros U - 590k

I think it is a bit early to pretend that those games will change the PS4's situation in Japan, as we've seen with the WIi U that this didn't happen with games of similar sales. Plus KHIII seems like it will be a late-gen release, and Persona 5 is a multiplat. Final Fantasy XV is the only game that should make a big difference, other than DQ:Heroes (which should also sell a decent amount.) 

Meanwhile the Wii U has plenty of future releases that should do well in Japan too. I'll bold a few. 

Future Wii U releases

Mario Party 10 (Mario Party 9 sold 750k in Japan, Mario Party 8 sold 1.58 mil.)

The Legend of Zelda ( 3D Zeldas sell about 700k in Japan.)

Animal Crossing U (City Folk sold 1.32 Mil in Japan)

SMT X Fire Emblem ( Radiant Dawn sold only 170k, but the Fire Emblem series just had a rejuvination in sales, the last game selling 520k in Japan.)

Xenoblade Chronicles X (Xenoblade Chronicles sold 170k in Japan, but it looks like the successor should sell more as it is getting a lot more of a media push.) 

Yoshi Wooly World ( Yoshi sells about 200k to 1 mil in Japan depending on the game.) 

Kirby and the Rainbow Curse (Kirby sells about 300k.) 

All of these games sell at least as well as Persona games do, so you can't disregard them. 

Also considering how they're not all RPG's, like the aforementioned PS4 lineup they will target more diverse audiences. 

Let's not forget it has to outsell wii u consistently, something that won't happen due to wii u's releases, pricecuts, bundles and holidays.