IME, primaries in SM (especially if the socioeconomics of their area are not absolutely dire) tend to rebound quicker than secondaries do - smaller ship to turn around, basically.
Also, for primaries, the conversion to an academy is less of a foregone conclusion. Primary academies are rarer than secondary ones, and depending on the LEA the pressure to academise may be resistable.
However, the head is very likely to be replaced. Often an executive head - sometimes, but not invariably, a head from a local school which is doing well - will spend some time in the school before a new substantive head is appointed. Often, major unpleasant changes - replacement of staff etc - will happen under the executive head, then the substantive head will be appointed to cement the rebuilding of the new team.
Significant staff turnover is likely - one school I know of has only 1 teacher who was in place before the Ofsted still in position 10 months on, all the rest (teachers and TAs alike) having left or been replaced. In another case, where there was a history of a staff / head split which lay behind many of the issues, the staff team re-grouped behind the executive head and only 1 teacher left.
the road ahead may be rocky, depending on how entrenched the issues leading to low results are. If entrenched, the school will not be able to turn round results for this academic year, and this will mean that it will take until July 2015 for substantially better 'formal' results to come through. If it's more of a short-term decline (e.g. a specific weak teacher in late KS2, or something which can be rapidly rectified once identified such as a lack of opportunity to write at length) then results may look up very quickly and the route out of SM will be quicker.