Well, this still has to be approved by FIBA, and supposedly for them to approve it, they would need to obtain permission from the Nets, since Williams is under contract. So, unless Prokorov wants to really rile up the other owners, by setting a major precedent that does a lot to hurt their bargaining strength, this won't go through.
On the other hand, letting Williams do this could give the Nets some good will when it comes to getting Williams to resign, and I have a feeling Prokorov is not a fan of the hard liners in this lockout, and could decide to basically tell them to screw off...which could have real implications in the negotiations, although I am not sure whether they would be good or bad for the chances of us seeing the NBA anytime soon.