The news is well known by now.
There will be a Motu Proprio issued (soon) that will transfer the jurisdiction over certain types of cases involving particular marriages and their validity from the CDW to the Rota.
That's the factual part of the news.
Then comes the speculation about why... and this is where one needs a rather large grain of salt on hand. The "informed sources" say that the CDW will be devoted completely to the issue of liturgical reform...the Reform of the Reform.... The New Liturgical Movement....The Hermeneutic of Continuity....whatever else it has been called. This is certainly a possibility and would fit in with several bits of information that have come out over the past year, particularly the rumored formation of a distinct emphasis within the CDW on Sacred Music and Art. It was never made clear if this would be an actual "office" or "dicastery" or whatever... but if that was true, then the rumors about the CDW's new role would make sense too. Such a group within the CDW would be necessary if the single purpose of the CDW were to be liturgical reform.
But this is speculation, not any kind of fact. The best we can do is wait and see what the Motu Proprio says. And even then...and even IF the CDW is so tasked, the real question is not what their new assignment is, but rather what their first actions in regard to that new assignment are.
It needs to be an out-of-the-park homerun.