That might be the right decision, but it wouldn't be the one I'd bet on hearing. Much more likely that if F35B gets canned so do the carriers and the Air Force gets a reduced buy of -A's.
Seems like a somewhat pessimistic situation to me, and from what I've heard coming out of people down in the MoD, at least one carrier was always a favourable option. And if the carriers get binned, then that'll be money that has never been wasted on such a colossal scale before.
The more likely option, if the B gets binned, is a typhoon/F18 fast jet fleet.