You would think that most schools have done about one or two assessment tasks by now? So perhaps it would be based on these in a worst case scenario. Given the government is predicting to hold onto these restrictions for around 6 months, I reckon the most likely outcome is that it would be safe to hold HSC exams by October/November but internal assessments in the meantime would need to be conducted in some online format or not conducted at all.
Many schools have chosen to suspend assessment tasks so have only one set, and furthermore many chose to hold so called “depth studies” and the required “mathematical assignment or investigation style task” in the previous term. As you may imagine, these tasks do not assess the content outcomes of the syllabus as well as as exams.
These restrictions will be in place for at least 6 months and possibly more, depending on how the situation evolves, and likely coincides with the period of remote learning. As can only be expected, online learning is substantially less effective than in school learning, and in light of this it is possible NESA will choose to reduce the syllabus and increase the weighting of their HSC exams.
Holding online exams is fraught with problems, the most critical of which is ensuring the integrity of the examination. Realistically, in the home setting students will find ways to cheat, even if they are under live surveillance. Additionally, online submission limits what can be tested, such as almost any working in math, as certainly you cannot expect students to learn LaTeX.