The US is using a 155mm gun on one class of vessel, and there are only three of those ships being built, so there will only be six such guns. They are expensive, but they will work very well shooting PGMs a long ways and directly for support of troops on land. They will be very accurate and have a very high rate of fire, being able to shoot many rounds from different angles and elevations depending on weather conditions so they all rain down on the targets at once.
I think the AGS may yet see production yet. There is a smaller size AGS BAE has proposed to fit onboard burkes to replace Mk 45s. It has slightly reduced performance such as rate of fire, but uses the same LRALM munition.
That is what they are designed for. Anti-shipping duties are possible with these weapons, but with the 80 PVLS cells and the Tactical Tomahawks for anti-shipping duties, there use for that mission will probably be very limited.
The USN is also developing the impressive LRASM-A, a stealthy long range AShM. A shame the USN gave up on LRASM-B, which would've provided a supersonic AShM like brahmos and YJ-12.