JTO is right.
Block 4/C2D2 is going to be entertaining as the international customer governments (whose F-35 project offices have been singing them the company song for years) turn over the MAKE GENERAL REPAIRS ON ALL YOUR HOUSES card, and find out that they have to pay for not only the new processors, but the new EO-DAS, the new EOTS, new CNI, the new... whatever. Because eventually the S/W that rides on the TR3 will expect to see that new H/W. Not to mention the updates to the US-domiciled, US-controlled reprogramming labs that they've paid for.
By the way, this is not a bug but a feature.