Having said that there very well could be a F35 D,E and F model emerge
First There most Definitely will be F35D,F35E and F35F Which will include newer engines upgraded systems and weapons.
but those are not what this is about I think.
now just like all of the models before it in other words the services won't be bound to just one model you could see a dedicated ground attack bird for the Marines a dedicated strike aircraft model for the navy and a multirole aircraft for the air force with the emphasis on air suppierorty all Could share common parts where possible and software also
I think you have missed a major factor here.
The Marines don't want a dedicated Air to ground bird. They want a multirole bird. if you look at there air load out the only dedicated CAS bird they have is the AH1Z, Otherwise the vast majority are F/A18 C-D and AV8B are intended to flex between Air to air and Air to ground.
The Navy wants Multirole
The USAF wants Multirole, The plane The F35A is replacing is not a dedicated Air superiority bird, it's a multi role fighter the F16. The Dedicated Air to Air birds the F15 and The F22.
Where you might see more flex coming in here is That the Airforce and Navy don't always buy the same weapons. The Marines want a Pure fleet of Fast Fixed wing to replace all there birds save perhaps the F5. Among those birds the EA6 which has been slowly phasing out. but the Marines unlike the Navy are not buying Growlers so they might want a new EW bird.
The Air force might also want one.