Here is the longer answer.
CEO Stephen Elop joined Nokia from Microsoft
. He is close to Microsoft CEO Steve Ballmer. A lot of us believe that his primary job at Nokia was to get the company close to Microsoft. And he did exactly that. Dumped MeeGo and partnered with Microsoft for Windows
Phone exclusivity for the near future.
I am not sure if the deal is official. Reports say that it would last for a few more years (2015 or 2016). Microsoft gave Nokia a lot of benefits as part of the deal. Financial help to the tune of 1 billion dollars over a period of several years and so on.
Things do not end here. Microsoft and Nokia have collaborated on their patents and they are leased out to competing companies for a price. This also ensures that Nokia would find it quite hard to detach itself from Microsoft.
Ballmer has said several times that they have not given up on the idea of launching devices based on competing platforms like Android
but it is just talk. Nokia is unlikely to launch Android based devices as long as he is the CEO of the company. So basically, Nokia board would have to decide whether they have had enough of Elop’s nonsense which is killing the company and start fresh with Android or Tizen or Firefox OS or Ubuntu Touch or whatever.