Hardly inevitable, for one, the RAF do not require a refuelling boom, not the method it uses for AAR
So if they did come from Mobile, (not that there is any political objection to that), they'd be producing two distinct models.
Plus at least some of the RAF machines, will likely be ex airliner conversions.
They'd end up with two distinct models in a small fleet.
So I do not see it as likely.
I can see that Airbus could eventually shift all A330 tanker production to the US, but won't they want to be totally focused on building and delivering to the USAF
for some considerable time?
They have set themselves a challenge here, after the unexpected USAF
choice of Airbus, they will not want to introduce any complexity into this operation, at least until USAF
deliveries are well under way and going well.
They have enjoyed a major coup, from the most demanding of customers, in a politically charged deal, why risk anything here?
So we have the question of time-lines not matching what the RAF requires (in fact desperately needs), if they come from the US line.