Would the Wii U be in a much better state if MK8 released last Christmas?

[Experimental42]

No.

I think the better question should be, would the Wii U have been in better shape if it had been released just before last year's Christmas.

Spoilers: Yes.

The problem with the WiiU is that it came out too early, with no real titles, and was labeled as dead by the time its competition even arrived. If the Wii U released at the same time as PS4 and Xbone, all the PS4 vs Xbone articles we were all bludgeoned with would have been PS4 vs Xbone vs WiiU articles because no one in the media is just going to ignore a Nintendo launch like they would a dead system.

On top of that, think of the launch lineup Wii U would have had with NSMBU, Mario 3D World, ZombiU, Pikmin 3, Wonderful 101, Nintendo Land, Monster Hunter, some Sonic games, and Windwaker HD, and then they announce that within the next year you'll also have the releases of Donkey Kong Country, Mario Kart 8, Super Smash Bros, Bayonetta 2, and Hyrule Warriors. Suddenly the Wii U is a competitor by virtue of its launch lineup alone.

The WiiU is simply an example of how important timing, marketing, and generating media buzz is for a successful launch, highlighting these things by completely lacking in all three.

As for the debate about Mario 3D world, the game was amazing, and its sales were only lackluster because Wii U sales were abysmal. Same for if the new Mario Kart does fail to surpass any of the others in the series: It's arguably the best but it's trapped on a system with the smallest units sold.