I'm a bit skeptical of this...I don't really know enough about the program. But last I heard it hasn't even finished testing....
"Gen. John Jumper"
Great name for a buyer of STOVL aircraft!
Depends on what you mean by "testing." The initial testing, to decide A) which plane they were going to pick and B) how well the basic design works of the one they chose, has been done. Lockheed/Martin won out over Boeing. The X-35 became the FA-35 and began the actual procurement process.
Each service committed to a basic number of units in each of the 3 variants (conventional for Air Force, carrier variant for Navy and SVTOL for Marines) and the manufacturer began early production of acceptance models. These models are used for the testing you're probably thinking of. They really never stop doing this type of testing throughout the life of an airframe. They're still doing this for the F15 and F16 for some issues.
From what I understand from talking to friends who have been involved in the process they tend to refine manufacturing, assess the exact parameters of the envelope, insist on hundreds of really stupid and expensive changes in the design... you know, the usual. That doesn't change the fact that this model has been accepted as the one they're going to buy. They're working out details. Realisticly they mostly involve manufacturing and maintenance issues.
This change is the Air Force shifting their own mission priorities. They've been trying to kill the A-10 Warthog for years. It's not a fast mover, it is, frankly, slow. It's ugly. It's also hell on ground targets and incredibly survivable. What it definitely is not is sexy. A SVTOL craft that can replace it, however, is sexy.
They need to do something convincing in this space if they want to kill the A-10, otherwise the law will be changed to allow the Army to fly fixed wing aircraft (that's right, there's a law that says the Army can't have fixed wing aircraft) or they have to turn that role over to the Marines. Neither prospect is attractive to the boys in baby blue.
in case you missed it, NOVA on PBS had a good (2-hour?) episode about the
Lockheed-Marting vs. Boeing "shootout" for the advanced plane design:
http://www.pbs.org/wgbh/nova/xplanes/