All other MLS teams will have to either have a partner in USL Pro or have a Reserve Team in USL Pro. So will NYCFC have to do one or the other OR will they get a pass since they are just starting.
Why would they? They'll have had almost 2 years to build their team and a relationship with a USL-Pro team. They'll also have players at the bottom of their roster that won't be getting regular playing time that they are looking to develop.
I would assume that NYCFC will have their own Reserve Team in the USL Pro division at some point since the owners have emphasized "The City Way" so much during the hiring/training of Kreis in Manchester. Whether this would happen in 2015 might depend on the stadium situation to a certain extent since a temporary MLS venue (ex: Yankee Stadium) might not have enough open dates for both the MLS and USL Pro teams
How hard is this really? If MLS does enforce the "must affiliate rule"; NYCFC grabs new Charlotte or Tulsa or AZ or OC Blues or possible St Louis or Detroit USL Pro club and loans some players out. Or maybe they start the new Westchester City FC USL Pro team. And if MLS doesn't enforce it, NYCFC does whatever it wants. Easy peasy.