With several new ready-to-drink cold brew coffee products in the pipeline and a growing retail footprint, private equity-backed Stumptown Coffee Roasters is betting on a big future for the hottest thing in cold coffee. The 14-year-old Portland, OR, coffee roaster and retailer is oft-credited with popularizing cold brew-which it began selling it in 10.5-ounce, ready-to-drink "stubby" bottles in 2011.