To be clear, I was not suggesting it would be over by June. Just that 18 June 2020 is the end of the current period for the "human biosecurity emergency" declared by the GG, and therefore the earliest that the travel ban is likely to end.
Note that a Declaration can be revoked by the G-G at any time, so the current expiry period is not a particularly good guide to when the restrictions will end. There will be a lot of pressure on the Australian Government not to let the restrictions continue in operation beyond the period during which they are strictly necessary, so it is likely that they will be under constant review.