If there are no places then decisions about moving her or not are pointless.
Sort of, I suppose, if no place ever comes up (or doesn't before the CAF deadline, as a school move after this, not necessitated by a change of address, and then normally only up to a few weeks later, may only change the DC's ranking after national offer day, with no guaranteethat a place would be availablebefore September), but not necessarily. If a place does come up, those who are on the waiting list / continuing interest list at the time will be ranked according to the school's oversubscription criteria land the place offered first to the child at the top. Or the only child on the list, if that's the situation, but no-one will be on the list who hasn't formally applied. So by applying now for year 5, and renewing interest, if required, at the appropriate time for placse coming up once the cohort moves into year 6, the OP will be in a position for their DC to be considered.
(Schools are not legally obliged to hold a waiting / CI list at all, but most do, ime).
N.B. the rules on a change of school vis à vis the submission of an on-time application for secondary would mean that starting the process now would be sensible, rather than waiting.