I'd say 99+ is still possible, if you get say 95+ in your other subjects and 87+ in English, that's still in the region of 99+. I think you just need to get a score past the median (as I suspect the median ATAR is around 98-99).
High ranking schools schools are very hard to estimate, because we know that for high ranking schools, the standard is quite high and we know you guys perform well as a cohort. So even with the appearance of a low rank, the actual mark you get might be high enough for the ATAR you need. In actuality, we should really estimate you based on exam performance over rank, as the standard in higher ranked schools either equals or exceeds HSC standards.