It has been long noted by critics of the DDG-1000 program that placing all of these ambitious new technologies aboard one tightly integrated platform in one great transformational leap for military mankind has the effect of integrating all of their various technical and programmatic risks as well -- in my view, magnifying the total project risk of the effort well beyond the total risks had the R&D for each system proceeded independently. (Synergistic effects can work against you as well as for you, especially when it comes to managing project risks.)
The 155mm AGS is a gun system which will never see use outside of the DDG-1000 platform; and unless the Zumwalt Class supporters in industry and in the US Northeast are successful in bypassing the Navy and selling more Zumwalts directly to the Congress, there will only be three of these ships, and only six operational AGS gun mounts -- a far cry from the 64 mounts that would have been deployed had 32 Zumwalts been procured instead of three.
As things stand today, the greatest utility the 155mm AGS system has for the US Navy is to provide justification for claiming that the USMC's interim requirements for fire support have been covered.
Once AGS has been declared to have reached IOC, then the Navy leadership will certify that the interim requirements for fire support have been met, and will give no more attention to pursuing further advancements in conventional naval gun technology.
Once that piece of paper has been signed, then it won't matter to the Navy leadership if another 155mm LRLAP round is ever fired again for any purpose whatsoever -- more so if the Zumwalt design as an integrated platform fails to live up to expectations in some major way and the three ships are then quietly set aside to guard their respective piers.