I don't understand why some people are getting angry about Germany hosting in case Australia wins. We already knew that a European country would be the host and that most participating countries are not a desirable option for financial, political or other reasons. There aren't too many countries that would be willing or able to host and there was already speculation about Germany hosting weeks ago.
Australia would have significant influence on the show and at the same time the host country would have to share the cost. Of course, both the host country and Australia would profit from being able to advertise their countries internationally but the host country wouldn't have the dominant and exclusive role that it normally has.
I think smaller countries in financial troubles like Slovenia would love to host the show, if they won, but hosting Australia's show with limited possibilities for the host nation would be much less attractive.
The EBU knew all along that Australia would be one of the most likely winners, so they needed a plan in advance. Preparations in the winner's country need to start soon after the contest and they couldn't afford wasting months with looking for a suitable host.
I understand the reasoning that the country in second place should host but we don't know who that will be and if it will be a suitable or willing host, especially considering the circumstances. So should we then go down the top 10 until someone is willing to host? In this case, the contest might go to Russia or Azerbaijan again.
Germany is a logical choice because the country is able to host a great show as was demonstrated in 2011 and it has the financial means and organizational skills to do so next year as well. The fact that they only hosted a few years ago is a reason why they would be a good host and not the opposite. They have only recently demonstrated their ability to host and Germany can be much more relaxed about hosting Australia's show than a country that hasn't hosted the contest in a long time or even a country that has never won and never hosted the show. So it would be much easier for Germany to share the spotlight with Australia.
Germany is the biggest possible host country and I don't see a country that is a more logical choice. Eastern and Southern European countries are often faced with financial or political problems and the Northern European countries have all hosted the contest in recent years anyway while at the same time being much smaller than Germany. A larger country seems like a more reasonable choice than a smaller country. Small countries that cannot often organize international events would love to win and hold their own contest but organizing and financially contributing to someone else's show is much less appealing.
Among the larger countries, the only other choice I see is the UK but cultural ties are not reason enough to let them host the show. Someone here posted weeks ago about strong ties between the Australian and the German broadcaster and let's not forget that the BBC hosted the anniversary show. I can only speculate here but maybe the deal was that the BBC gets the anniversary show and Germany gets to hold Eurovision in case of an Australian victory.
Australia is one of the favorites but the way it looks now, other countries are more likely to win anyway.
If Germany could organize the show together with Australia, we might very well get the best Eurovision in history. There might be two Australian hosts and one German host, maybe Anke again. And last but not least Australia hosting the contest in Germany would make for much better bridge building than choosing the UK for historic reasons.