Pieter, a good question and the answer is not complicated but complex! There will be plenty of opportunity for racing in WA as I will explain.
Basically it goes like this, under the old system (1 Nationals each year) it would take the states with 4 or 5 tracks between 20 and 40 years to get the nationals on the normal rotation basis. I.e. say Qld has 5 tracks capable of holding the Nationals and all are interested in holding it.
Last year, 2014 Qld held the nationals at Meakin Park, therefore it would be 2021 before they come back to Qld (after it had rotated through all the other states) and the next club in the Qld rotation could hold it.
Therefore theoretically if all clubs in Qld opted to hold it when it was their turn then Meakin park wouldn't get it again until 2042
Under the new system there is the equivilant of 3 Nationals each year, with 3 states holding them each year. This means the rotation comes around a whole lot quicker, i.e. in 2 years all but 1 state will have had a round of the Nationals.
Therefore WA I'm led to believe will get a round of the Nationals in 2017 and the other rumour and it's just a rumour that I've heard is that FEMCA may come back to MORBC in 2017 as well! Therefore possibly 2 big events for people to get some practise in leading up to the rumoured worlds in 2018.
Remember the 2018 worlds qualifying takes place in 2016 and 2017. During the worlds year (2018) everyone will start qualifying for the 2020 worlds.