Like most jets F-35 is having its capabilities improved over time with the various Block upgrades discussed in the links in the many pages above. The discussion is really whether the 2B configuration is sufficient to give the USMC something useful when they declare IOC.
The USMC and LM say it does, others say it doesn't. For the UK we need to see what standard 17(R) Sqn are going to be testing on our aircraft, how they do during that testing and how the USMC are doing with IOC before we declare IOC.