Yes! It took a very long time (almost 2 years!), but Media Create top 100 (jan-june-2017) says that, Super Mario Maker is finally above the 1 million mark of sales on Japan allone! Congrats to Nintendo for this milestone!

075. [WIU] Super Mario Maker – 28.469 / 1.000.875 (Nintendo) – {10/09/2015}

Check the full list here.

Splatoon 2 will do this buy it's 2nd "week". No biggie.

Oh nice! Does this make 3rd or 4th Wii U Million seller in Japan?

According to VGC it's the 4th Million seller in Japan for Wii U.

#1 Splatoon (1.54)
#2 Mario Kart 8 (1.34)
#3 New Super Mario Bros. U (1.29)
#4 Super Mario Maker (0.99) (as of June 11th)

The next ones would be
Super Smash Bros. for Wii U (0.84)
Wii Party U (0.84)
Super Mario 3D World (0.75)

I think we won't see another Million seller on Wii U. The highest selling Wii U title in Japan is Zelda BOTW, which has sold 2'003 copies the week of June 11th and only 0.13 Million copies in total, by the way.

What is the lifetime sales of WiiU in Japan? I believe around 5M? if so, those numbers aren't that bad. Glad that the WiiU got another million seller.
I believe the 3Ds version sold a million as well?

Its arpund 3.5mil

Always nice to see a milestone passed especially for such a good game. Wonder if we'll get a switch version in the future.

Wow, for a home console in Japan Wii U sure got a nice amount of 1 million sellers.

Indeed. The PS4 doesn't have any Million sellers in Japan right now. Final Fantasy XV is at 0.98 Million, and MGS V and GTA V on second and third place have only half a Million sold...