The LCU replacement is called SC(X)(R) (for Surface Connector Replacement) and the design is still under consideration. Given the growing cash shortages in the navy, it’s likely that the LCU replacement will just be an updating of the existing design. LCUs were developed during World War II and are still in wide use by nations that have a lot of coastline or nearby islands.
In the 1990s, the U.S. Army replaced its own fleet of LCU 1600s with 34 LCU 2000s. These are 1,087 ton ships that can carry 350 tons (or up to five tanks or 24 cargo containers). The LCU 2000 has the same size crew but can stay at sea for up to 27 days. The army stations some of them overseas (Kuwait, Japan) to help move cargo from anchored ships to shore (and up rivers or numerous bases). The navy may end up following the army lead in choosing an affordable design for its LCU replacement. The navy would like something more exotic but the cash just isn’t there. The army LCU 2000s have been in service nearly two decades now and the army is planning to refurbish them so the ships can serve another decade beyond their designed life of 25 years. If the navy wants a low-risk replacement for its older LCUs, something based on the army LCU is the best candidate.