So uh, let me be the first to post an educated reply here.
It's not likely Minecon 2017 will be held in the USA. As many know, Mojang tends to have USA --> Europe --> USA trend, so I would expect it to be in Europe for 2017.
I don't believe it will be held in Australia. Australia is too far and expensive for many people to travel, and according to http://www.develop-online.net, Australia is only number 6 on the top 10 countries that play Minecraft. The first two being USA and UK respectively. According to the past 5 Minecons so far, Mojang has also chosen not to repeat locations, meaning that it is also very unlikely it will be held in London or Paris again.
My guess is that Minecon will be held in 1 of 3 locations. Belgium, The Netherlands, or Germany.
A. These countries are located in Europe.
B. These countries have populated cities such as Brussels, Amsterdam, and Berlin that have not been locations of Minecon in the past.
C. All these locations are relatively safe.
I personally have been to all three of these locations, and in my opinion, these would all be great spots for Minecon to be held as well.
So yeah, do with this information as you want, but this is how I feel.