One thing is glaringly obvious about the Coast Guard's medium endurance cutters: they are old. Real old. According to the Sixteenth Edition of the Naval Institute Guide to Combat Fleets of the World, 15 of the Coast Guard's 28 medium endurance cutters are over 45 years old, and only three of them were commissioned after music superstar Taylor Swift was born. You could say they are due to be replaced.
Fortunately, the Coast Guard has been working on a replacement. They call it the Heritage-class Offshore Patrol Cutter, and according to a handout WATM obtained at the 2018 SeaAirSpace expo in National Harbor, Maryland, it will be replacing all 28 of the medium-endurance cutters currently in service.
A Reliance-class medium endurance cutter. Most of these ships are over 50 years old.
These cutters, the first of which will be named USCGC Argus, will pack a 57mm gun (like the National Security Cutter and Littoral Combat Ship), as well as be able to operate a helicopter. Globalsecurity.org notes that the cutters will displace 3,200 tons and will have a top speed of at least 22 knots.
The Coast Guard currently operates 14 Reliance-class cutters, from a class of 17 built in the 1960s. Three of the vessels were decommissioned and transferred to allied navies. These vessels displace about 879 tons and have a top speed of 18 knots. Their primary armament is a 25mm Bushmaster chain gun, like that used on the M2 Bradley.
A Famous-class medium endurance cutter. These vessels can be equipped with Harpoon anti-ship missiles and a Phalanx close-in weapon system.
The other major medium endurance cutter is the Famous-class cutter. This cutter comes in at 1,200 tons, and has a 76mm OTO Melara gun as its primary armament. It has a top speed of just under 20 knots, and is also capable of carrying two quad Mk 141 launchers for Harpoon anti-ship missiles and a Mk 15 Phalanx Close-In Weapon System (CIWS).
Finally, there is the Alex Haley, an Edenton-class salvage tug acquired by the Coast Guard after the United States Navy retired the three-ship class. Two sisters were transferred to South Korea. It does remain to be seen how 25 Offshore Patrol Cutters can replace 28 older hulls, though.