Based on no hard data whatsoever, I think that the WSMs are here to stay. They seem to be gaining traction, being added to the lineup of more manufacturers this year. The 270 and 300 WSM seem to have the best chance. The 7mm might have too much entreched competition from existing 7mm rounds to make it in the long run.

I'd be interested in seeing some sales figures from Browning, Winchester, and Remington on how many of what caliber's they've sold in 2002. While the early adopters may not turn into sustained interest, it'd still be worth seeing some hard numbers.