These new dates are a formality needed in order for the program to secure continued funding.
The Navy date is interesting for a number of reasons. That aircraft has to prove that it can launch and trap on an aircraft carrier along with passing the Navy's operational certification known as an "OPEVAL".
Note also that the USMC has signed up for 80 F-35Cs. It is interesting that one would think that, the C is less complex than a B and even if its carrier qualification was not done, USMC C-models could fly from land bases until (or if) they get their act together. Note that most Harrier operations have been from long airfields.
The other challenge for all services is the question of close air support. There are the issues with the helmet-cueing and early software blocks used by the USMC and USAF for their early IOC. The early blocks will not support the gun-pod (USMC) or much else.
The wars over the past 11 years or so have created a much closer control of close air support attacks. There was the situation where a ground controller brought authorized a JDAM strike on his own head. Another time, Air National Guard F-16 pilots bombed Canadian ground troops in Afghanistan based on a very weak process of target verification. Those are only two of several blue-on-blue incidents.
Close air support today is controlled by a specific briefing/checklist with all items that have to be ticked off on and agreed to by the ground and air partners. ROVER, a kit that--among other things--allows the ground forward air controller and bombing aircraft to share images from aircraft targeting pods is now common doctrine to improve safety and mission success.
The block software path of the F-35 brings this all into question.
The gun for straffing, like it or not has been used many times in the recent wars. A 500 pound bomb has a different safety distance from friendly troops compared to cannon rounds from an aircraft.
For example, in a low threat environment, the USMC Yankee and Zulu helicopters, combined with the USMC C-130J Harvest Hawk, give a Marine and/or Joint commander many more options. The Harvest Hawk can be a cargo aircraft, an air-refueling tanker, or a ground attack and ISR aircraft as needed.
Note also, in the case of the USMC and Army, they have a good variety of artillery options. And for the Army, the Apache helicopter is an outstanding, night, net-centric, close air support aircraft.
Recently, the USAF stood down several flying squadrons. One F-15E squadron that was stood down (for the rest of the year it looks like), was fully combat capable, came back from a successful combat deployment and is its combat capability is now gone. For every month it is deactivated, it will take another month to get it combat capable. So even if it is funded again by the next fiscal budget it most likely will not be combat capable for another year after after funding takes effect.
The F-15E has incredible range, weapon versatility such as JASSM for long range stand-off, and other precision weapons. With its' two-aircrew, the aircraft has shown, over and over, it is valuable for close air-support. The F-35B, that the USMC wants so bad... for its' prime mission of supporting troops on the ground...will not be capable of doing this.
The F-15E is one of the few aircraft (besides long range bombers) that has any relevance in a "Pacific Pivot".
When a general or admiral stands up and states that we need the F-35, they are not being honest with the taxpayer.
