I really am starting to suspect that Mario Kart 8 was moved to that awkward May 30th date to save Iwata's bacon at this shareholders meeting of confidence in June.
If they released the game in March/April as was planned, it would give time for the game to spike Wii U sales, but to also then inevitably the spike would dissipate and Wii U would normalize in sales as almost any platform does a few weeks removed from a big game.
But by moving the release date to May 30th worldwide, investors won't see the downcycle of that trend, they'll only be shown the first week or two of sales of Mario Kart 8 and Iwata can say "see? Wii U is doing better, have patience with me".
It's kind of disingenuous to be honest and it would be pretty lame if they made us Wii U owners wait an extra few weeks so that Iwata could use the game for corporate politics like that.
There's not much he can do about the Wii U IMO, I think that Quality of Life is going to either save him or flop, if it flops I think shareholders will become extremely angry and vote him out or force his resignation. Right now I think he's trying to just buy himself time, by promising QoL next year -- probably convienantly next May/June launch as well, so investors can't really judge its performance properly for the June 2015 vote. It will buy Iwata another year of time to keep stringing the investors along.
