In an interview with Sakurai:

What was the reason to make the Nintendo 3DS [version of Smash Bros.] before the Wii U [version]?

Compared to the 3DS [version], the Wii U [version] is larger in scale and also has many modes so the production takes time. It is that simple.

There are fighters that got their Final Smashes changed and fighters that didn’t; what is the reason for this?

It differs depending on the case. Lucario['s final smash changed] because Mega Evolution was introduced in the latest installment [of Pokemon]. Pit because Palutena turned into a fighter. Moves, too, were modified due to balancing and elements of the new game were factored in.

Are there any interesting things in pictures from during the development?

There are many… The Flying Men of 3DS stage Magicant are expressed as pixel sprites, but actually a 3D model was also produced. A pixel sprite was chosen since it has lower strain [on hardware].

http://nintendoeverything.com/sakurai-on-why-smash-bros-3ds-came-out-before-the-wii-u-version-changes-in-final-smashes-stage-tidbit/

_________

So what I get from this is that there are more versions in the Wii U that have yet to be annouced... Or he's just referring to the same modes that are also in the 3ds version...

Hopefully there are.

I hope so cause the wiiU version is looking like the "Definitive" Version

It was always looking like that ofcourse.

True but I was mostly expecting it with just better graphics and music and maybe one exclusive mode but there seems to be a lottttt more than just that which makes me glad!

Sakurai better not be fucking around.

Board Game, Stage Creator, Master/Crazy Orders and Amiibo (for now) are all Wii U exclusive....so yeah

We didn't know this??? :0

It should be a given considering it isn't limited by hardware as the 3DS is.

It wasn't confirmed so no :P