I would hope that if VCE exams were to be cancelled, you'd know this by the start of term 2 (or cancellation of term 2). If they're cancelled (and I hope for your sakes that they're not), I wouldn't be too surprised to see a big increase in the alternative entry options offered by uni.
Logistically it'd be a nightmare to cancel year 12 - how do schools (many of which are already bursting at the seams) cope with an extra year of students? How do unis cope with losing almost an entire year of students (imagine graduation ceremonies in four years time haha).
I do agree with you about how rural schools will be far more disadvantaged by this. However, I think that with measures like accounting for whether people have wifi at home, and existing measures like location disadvantage & education level of parents, I don't think it'll necessarily be worse at accounting for disadvantage than the system currently is - That's not to say that seas is going to be able to compensate for the disproportionate effects of covid-19, just that it already does a shit job of accounting for all disadvantage.
It is true that there are some young and otherwise healthy people who get seriously ill from covd-19, however I think it's been played up a bit to try and scare young people who otherwise wouldn't care into actually practicing good hygiene, we're still a tiny fraction of serious cases.
Also, with schools potentially going to online mode, it will again affect students. A portion of students would probably prefer face-to-face learning and maybe they'll find online learning too difficult to them or hard to adjust to as they are not used to it. Again, this is another factor that will ultimately affect their learning.
Same could be said in reverse so I don't think this is a big deal - definitely something that ses will effect as high ses people will be able to afford tutors and more likely to have better educated parents who can help them but that is how it is with regular school too.
Covid-19 is definitely going to exacerbate a lot of disadvantage - It's pretty much certain that there'll be increased rates of domestic violence, a lot of people with existing mental health illnesses are going to struggle with isolation, and those without are going to be at increased risk, people who don't have a home environment that's a good learning space or don't have the resources they need to study are going to really struggle with the closures of schools along with libraries and other public resources. It's a whole lot shitty all around.