I can't predict the future, but I'd be very surprised if Remington ever re-intorduced the XP-100, particularly in the mid-grip version. They were dropped years ago due to lack of sales, and even the repeater version didn't sell well enough. For today you can get a new mid-grip Savage Striker in a variety of chamberings including the .300 WSM...for as long as Savage still offers it anyway; it isn't on their website any more.
A WSM chambering for handgun silhouette would be a big mistake, 'way too much recoil and target damage. Even a factory .308 load is too much. I shot a whole lot of 40x40s with my little .30 Herretts, and very seldom rung a ram under the old rules.