This seems likely, however, it would mean the resumption of the guerilla war. It would take a lot of effort to wipe out the insurgency, it also begs the question of who will lead after? I can only assume that it would a coalition between moderate natives and the army (which was mixed). At this point white rule is gone for good without something drastic occurring.Operation Quartz would've been an overwhelming victory for Rhodesian forces, as the insurgents had largely come out in the open and gathered in around 11 spots; Operation Dingo showed what happens when this occurred and the Rhodies struck.
If it fails, however, possibly due to a British tip off, things could get really bloody. Mugabe is a head case and certainly has no love lost for the White Rhodesians. If it devolves into fighting on the streets it would be easy to see massacres of Whites and anti-Mugabe blacks if Mugabe can gain control of Salisbury. SA wouldn't stand for it, intervention seems almost guaranteed. Though whether that would involve an attempt a step restoring minority rule or by crushing Mugabe and evacuating the whites would take someone with a better knowledge of SA politics to answer.