If you are wondering how long Microsoft is planning to support a particular technology, then take a look at their product lifecycle search engine. It will tell you both the mainstream support end dates as well as the extended end dates. If you take a closer look at the support dates for some of the technologies such as Microsoft Silverlight, then you can also quickly figure out which technologies Microsoft has decided to drop.
Here is the link to the Microsoft Product LifeCycle Search engine
Justin Cooney 