But Sony and Microsoft are not really trying for those. And even if third parties are, it's also just as likely they will fail for the same reason they couldn't get a strong foothold on the Wii.

If they try hard enough they won't fail (in the sense they won't lose money), but I can agree that the current installed base could give good games for WM Plus a good but not overwhelming success, while initial installed base will allow at most decent success and nothing more for Move and Kinect games and the two new platforms will need at least one year of good sales to allow their games the potential success a WM Plus game can hope for right now.

Edit: BTW, from the infos we can gather, we can say Sony did really well regarding HW, but still has a lot of work to do for SW and marketing, while MS is working hard on marketing, but still cutting sorry figures due to bugs, and having cut corners to save on HW costs it got a lot of unpredicted troubles on drivers, and, just like Sony, still has to work on SW too. In both cases, they made considerable investments, so the undeniable fact that both are lagging behind in one or more fields is really baffling, unless both be repeating their old errors, Sony pretending to succeed just by HW excellence and MS by marketing.