South Africa for me, although they didn't make your list. Based on the assumption that their coaching lineup will improve and adapt to more open rugby they are trying with their Super Rugby teams or be replaced at the end of this year if they don't.
I guess the climate will be quite European in nature come September 2019, so I'd put Ireland as my next choice. Although Chieka will doubtless wring out a performance from his increasingly threadbare Aussie squad.
I'm not sure I'd make England a top two favourite, but I expect them to progress from the group stage this time despite not having home advantage this time.