As already stated above, your question has been brought up numerous times in the APN, CNS and NP forums. There is no formal mandate to change the requirement from master's to DNP by 2015. The American Association of Colleges of Nursing is "recommending" the transition and many of the member schools have followed by offering the DNP in their campuses. There are some institutions that made announcements that they will be phasing out their master's in a specified time frame but this is not the majority, in fact, some schools have not started offering a DNP program yet.
Education is only one part of entry to practice as an NP. The other piece is national and state certification. The national certification boards have not made any announcement that they will only certify DNP prepared NP's after 2015. In the same vein, no state BON have made similar announcements that will limit NP certification to those trained with a DNP after the year 2015.
To answer one of your questions, the FAQ's on the DNP at the American Association of Colleges of Nursing website did not provide details on how the grandfathering of master's prepared NP's will be carried out. It is a hope of master's prepared NP's like myself and students who may be caught between the transition, that we are advised accordingly if this recomendation becomes mandatory.