However GBallzack both FF13 and MGS4 are popular enough exclusives to matter. I realise this Im just claiming that they both 'might' be ported or have some of their thunder stolen by bad press about the PS3.
I think a 90M lowest estimate for the Wii is ridiculous though =$, each to their own I guess.
Edit: There is a good deal of rumour about FF13 and I think MGS4, people think it could end up being ported if the PS3 doesnt have enough of the market to recoup their losses. I think its unlikely, but we are talking worst case here.
Nintendo's big IP's are first party so they couldnt be hit by such a bombshell.