By now, you should have heard of the announcement of Nokia's collaboration with Microsoft to put their Windows Phone OS onto their devices. The following are some of my thoughts on how this collaboration will affect mobile developers.
This is definitely a win for Microsoft. Having a partner strong in hardware is definitely going to drive up the reachability of the platform. And Nokia has always been good in their hardware, hence Microsoft will get a lot of additional exposure, apart from the usual hardware partners like Samsung, HTC, LG, and others.
I am not sure if Nokia will win in the long run. In the short term, this may drive up the sales for it's hardware, but Nokia's pace will likely be dictated by the timeline of the Windows Phone OS. Whatever hardware innovations they have will be subjected to the support of the OS. We do not know the detailed arrangements, but I doubt Microsoft will customize the OS too much to suit each device manufacturer's request as other device manufacturers will also want the same treatment. Also, by this collaboration Nokia is directly jumping into the boxing ring together with the other devices manufacturers, and will now face the other very stiff competitors such as HTC, Samsung, LG, etc, who already have a head start in supporting the Windows Phone OS.
I think the overall success factor affecting Microsoft (and Nokia and other device manufacturers) is their ability to build a successful ecosystem. Having a good ecosystem will get people to buy your devices, and when people buy your devices, developers will come. This is very much a chicken-and-egg problem - there are no users if there are no apps, and if there are no users, there are no apps.
Personally, I would think that Nokia is buying time to get their MeeGo OS ready. This is very much like the early day of Steve Jobs' return to Apple, where he collaborated with Microsoft by bundling Internet Explorer with the Mac OS. In return, Microsoft agreed to invest in Apple and committed to continue writing apps for the platform.
Obviously, if you are a Symbian developer, this is really bad news. I don't think there is much you can do now, except to learn a new platform as soon as you can. The good news is that the Windows Phone platform is very easy to pick up. Experienced C++ and Java developers should have no problem in learning the .NET Compact Framework, which supports languages such as VB.NET and C#.
If you are a Windows Phone developer, this news could not be better - you now have a wider customer base to reach out for. If you have been hesitating to get onto this platform, there is no better time than now.
If you are an Android developer, there is little impact for you, as Android devices are already flooding the market today. And there is no certainty that Nokia might not look to Google for another partnership. Look at Motorola, their devices run on all sorts of platforms, such as Windows Mobile, Android, etc. Moreover, 2011 is the year of tablets, with the Motorola Xoom stealing the limelight at this moment.
What about iPhone developers? This is not going to change your world as you have enough devices to keep yourself busy for a while - iPod touch, iPhone, and iPad. And oh yes, the new iPad 2 will make things even more exciting, not to mention the up-and-coming iPhone 5.
In short, this year is going to be a very exciting time for mobile developers, only if you choose the right platforms to hedge your bets. For me, I am putting all my money on Windows Phone, Android, and iOS.
. With the new Apple iPad 2 and the new Android tablet by Google, the tablet market is set to explode in the second half of 2011 and beyond. And this is the best time for you to pick up the foundation skills so that you can get yourself ready for the next wave in mobile development. 
