Unmanned surface vessels are about to get serious. The Large Unnamed Surface Vessel (LUSV) is planned to have vertical missile launch tubes. The LUSV can accompany manned combatants and provide additional magazine space. This has great potential.
I'm sure there's plenty more development work needed to make this a reality.
The attached illustration is of one proposed such LUSV from Austal, the Australian firm that makes trimaran LCSs and EPFs. There are apparently three other companies in the running as well.
Note the kite or tethered UAV; I've not read of the explanation for such but it makes sense: If the LUSV is some miles away from the DDG or other missile ship, instant connectivity will be critical and getting an antenna well above the surface will be important.