I think you should release the social version first, let it find it's audience and then introduce additional features (like marketplace). I would suggest this even if you had the 2nd part finished. Also, I would inform users, in advance, of the upcoming features. I`m not sure what this app is, but generally speaking "surprising" monetizing related features can create user backlash. Be fair but not apologetic, show the value of your core product and of the upgrades to come.