When L2S came out I was fan and have been ever since, however there were some concerns of what was going to happen to it with EF closing in on its heels. As with any technology there is a couple of factors that can help make technology adoption decisions.
Meeting a need
Even though Support and Future can be the same the can also be different as in this case. For example, VB6 is no longer supported however it has no future either! L2S and EF are both supported however what is their future? Obviously, Microsoft has chosen EF as their primary ORM framework because it plays better with other non-Microsoft technologies, but L2S has less of a learning curve when compared to EF which makes it fairly easier when connecting to Sql Server. At this point a decision could be made based on which technology "meets the need", but as a consultant I think it is equally important on understanding how both technologies work and what features can be taken advantage of during development. Here are some of the changes that were added into .Net 4.0.
Post initiated from this Visual Studio article