The F/A-18C and D models are no longer deployed and have been replaced by the F/A-18E and F "super hornets" (which only share about 15% parts commonality with the C/D) and the F/A-18G replaced the EA-6B.
They're going to be around quite a while but the F-35 is their "replacement" but so expensive I don't think that it ever really will.
Not quite correct.
The F/A-18 A/C/D Hornets are still flying in USMC service - the last USMC Hornet squadron is due to re-equip to F-35s around 2030 (see USMC F-35 transition plan
There are still two USN F/A-18A/C/D Hornet squadrons - VFA-204
is a reserve squadron based in New Orleans, and provides adversary support for the Navy's Fleet Replacement Squadrons (FRS's) which train new pilots to fly the F/A-18E/F Super Hornet or the F-35 Lightning II at NAS Key West, Florida and NAS Fallon, Nevada. VFC-12
is a reserve squadron based at NAS Oceana, Virginia, and provides adversary training to East Coast air wings.
The F-35 is the replacement for the F/A-18A/C/D (and the AV-8B in the USMC). The USN has equipped some former F/A-18A/C/D squadrons with F/A-18E/F Super Hornets, and these will be replaced by F-35s over time - the planned final mix is ~50% F-35 & ~50% Super Hornets.
The F/A-18E/F will serve beside the F-35 for at least 2 more decades - the Super Hornets are supposed to be replaced by a new fighter beginning around 2040... which could be manned, unmanned, or "optionally manned".
Jon A. - Sgt, USMC 1981-89, A-6E & F/A-18 avionics tech