They might try to get that Nintendo marketshare but Sony is too. I find it unlikely that People who bought Nintendo consoles go to MS instead of Sony (If they buy another Console that is).
Don't take this too literally. It's just percentages. MS has new hardware launch, Nintendo doesn't. Sales of "xbox family" will grow more than those of the "nintendo family". As a result of that, Nintendo will lose marketshare in that month, MS will gain marketshare.
They won't convert potential WiiU buyers.
Checked Euro am Sonntag at a Kiosk to see if there are actual hardware numbers published. But it's just an article with investment tipps for the big publishers (don't buy TakeTwo) which is based on some publically known market studies.
Kaltner mentions Sony in the interview:
-"They go for volumes and marketshare and sell at a loss. We go for profit on day one."
- Xbox Germany is aiming to be profitable on day one, too
-"MS as a pure software company is "history". We want to sell hardware and dedicated software tailored specifily to that" (He worded it in a way, that it really sounded like they are aiming to be like apple)
- "We want to be woldwide number one, as we where with the 360" (It wasn't a predicition or a claim, don't take it too seriously)