I don't see it.
If they do swap out the bundle entirely, they won't drop Wii Sports, and more than likely bundle it seperately with a controller like they do with Wii Play.
If they do make a bundle with WSR, then I would imagine it still keeps WS in there anyway, or perhaps do some combinations with say, Wii+WS at a cut price ($200) then 2 seperate bundles both with WS included, but one with Wii Fit (or WF+) and the other with WSR... both at $250. (or if one has WF+ instead of WF then it may be slightly more, as balance board > than WM+)
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Either way... WSR wil never manage WS numbers. In the very best scenario for it, it could pass Wii Play and/or Wii Fit, but I highly doubt it.... in fact the likely scenario I see will involve it being round about Mario Kart Wii figures, so it may not even beat that.
And if it does poorly, I still see it passing 10 million, it would have to be a real bomb to not make 10 million..... which shows how huge this game is (bigger than GTA franchise IMO)