For now, Jason Collins will indeed report to the Washington Wizards, according to Gary Washburn of the Boston Globe:

gary washburn @GwashNBAGlobe

Always tough talking to guy who's been traded from potential playoff team to rebuilding team, Jason Collins said he will report to #wizards

It remains to be seen if that holds true or if the Wizards agree to a buyout with him. If Collins and Barbosa both stay on the roster, the Wizards will have 15 players under contract.