The logic of this split to makes sense to me - as long as people associate foursquare with checkins rather than discovery, it'll be hard for them to go head to head with Yelp.
But it's odd that they'd create a new app around checkins and continue trying to associate the foursquare brand with discovery. Wouldn't it be easier to keep foursquare as "the checkin app" (how people already see it) and create a new brand identity for "the discovery app"?