I believe it is the 25DD AKA next generation 5,000tonnes DD you are talking about not 26DD.We are aware that two new Atago AEGIS DDGs are proposed, and that the 26DD project is coming on behind the Akizuki.
We just haven't gotten into a lot of detail on it yet.
JMSDF plans on constructing 6 ships of this class to replace the remaining Hatsuyuki class. There are 8 hulls still in commission including 3 training vessels which will be replaced within the next 5~6 years starting with 2 hulls next year in exchange for the remaining two Akizuki class which will come into commission in March 2014.
Soon after I believe the Asagiri class DD will be decommissioned to be replaced with an advanced version of the Akizuki class. There are 8 ships of this class including two training vessels.
The reason for the rush is to unify equipment incorporating VLS onto all hulls to maintain combat readiness, no requirement for retraining of sailors during transition from one ship to the other and streamline procurement requirements as much as possible.
This is probably one of the biggest single lesson Japan learned from our own mistakes from the last war that Japan does not care to make again.