My Mum and Dad took a holiday to Burma earlier this year and were faced with precisely the same dilemma. For peace of mind, they decided to book a package through a travel agent approximately six months ahead of travel, even though there may have been the possibility of a saving by waiting later.
Following their booking I monitored the fares out of interest. As it turned out, there would have been no particularly good time to buy. Burma is probably a high willingness to pay market due to it's particularly unique character and relatively closed status. Furthermore, QR does not deploy a large amount of capacity.
There were some promotions in business class, including 241, but by the time they materialised all the sale-applicable fare buckets for the days they needed to travel were closed.
All that said, you are looking at flights nearly a year ahead. I doubt that you would lose out by waiting another six months to see if anything favourable happens.