So what are we going to replace our GR4s with? Typhoon I guess. So, how many Dave Bs will we need?
Courtney, I think the F-35B will replace both Harrier AND Tornado. It will have the flexibility to use the Harrier concept (to a degree) but with a range and payload more akin to GR4. As for your second question, it will be interesting to see how numbers pan out. With the initial requirement (Harrier 'like' replacement) comes a further potential requirement to replace GR4 FE@R with F-35 (possibly F-35A) so we could see a future buy of A models, though certainly not in this decade. So total buy (B and A model) could be higher than is currently being mooted.
Granted, a number of GR4-unique capabilities such as Storm Shadow will migrate to Typhoon initially however, the aspiration and plan to fit it externally to F-35 is there.