Navaleye has a point about the GR4s and it is one often raised around the stations but there are some real facts to consider:
First the RN badged Harrier squadrons are part of the force which is, to use an Army expression, tour plotted by the RAF. While the JFH are deployed for their stint the RN badged sqns take their turn (and turn) until the whole force is relieved. That is efficient use of resources and the date of relief will be promulgated when the force is used to the prudent limit of its endurance and not before. Thus an embarked requirement will not yet enter the fray.
What replaces JFH in the Stan remains to be seen - it could well be the mighty GR4; or some Typhoons in the mud role or more of Uncle Sam's aircraft (or those of another Ally but I'm ney holding ma breath on that one). Rather depends on the timing of relief.