"50m+ is improbable. Nothing ever sold that well."

Wii-motes have. The 50M figure was for total Motion+ sold not Sports Resort.

I doubt it'll hit 50M first year simply because of supply.

If M+ takes off, it will be bigger than the DS going Lite or the DSi.

How many WM+ will be sold, we'll probably never know. Or we'd have to wait for Nintendo's quarterly reports for that. Just as we don't really know how many WiiMotes have been sold. Do we know that?

The game bundle, on the other hand, that will be tracked on VGC, by NPD and all the others. I really doubt that will reach 50m+, unless, as you say, it's bundled with the Wii. Not sure that will happen, but hey, what do I know?

But really, the Wii Sports Resort figure is the interesting one, since it gives you a 'very least install base' figure.

Seems plausible.

If Wii Sports is Super Mario Bros., then Wii Sports Resort must be Super Mario Bros. 3.

It really depends if WM+ gets integrated into the Wiimote. I would put even odds that this will eventually happen.