It's probably not a bluff. They've pretty much saturated the U.S. market; there's not much room left to grow here. It would make more sense to focus their efforts on growing in other regions where they have plenty of headroom to increase their userbase and monetization. Depending on how things play out, they could match their current revenue in a matter of years and still have room left to grow. There's also the potential to re-enter the U.S. market down the line. Why would they throw that all away and essentially create their own competitor by selling their core technology and diluting/confusing their brand with whatever U.S. company they sell to?