The developments with DJ's products are always interesting. A couple of times a good idea seems to have had been implemented in ways which surprise me and don't seem to pick up on the lessons others have learnt.
AirNZ has reduced 737 and A320 seat pitch in both planes and reversed it the second time on the 737 back to a min of 30 inches. The lesson learnt seems to be don't drop below 30" and to sell the benefits of space plus while treating the basic economy seat of 30" as standard.
With the 738 I suspect there is room/scope to reduce the seat pitch of some rows down to 30", especially if they reduce the pitch of the blue zone (exit rows), as AirNZ did in the back half of the A320 economy when they went to 142 seat in economy. However AirNZ was a lot quieter about it than DJ are (having tried the layout at Freedon Air first). Actually DJ seems louder about the fact they are reducing seat pitch than I recall them advertising the extra seat pitch they have been offering above the competition.
To me the message should have been communicated as part of an overall product revamp and rebranding where it was sold as our most loyal customers and those on higher fare tickets get the better seats which have an extra 2 inches leg room, access to lounge, priority ... etc. All our other economy seats are industry standard (ie 30 inches) but we offer frequent flyer points, modern planes and a good choice of buy on board food etc.