I read an article recently regarding creating task based WCF service references in this article.
The mechanism that I use to generate my service references for consuming applications is using svcutil in a batch file.
Is it possible to create task based wcf service references with svcutil?
I haven't tried it yet, but it looks like version 4.5 of svcutil.exe includes Task-Based operations by default. You can use the "/syncOnly" flag to disable Task-Based operations. Source
Also, if you want to include task-based operations within Visual Studio, you can select that option when importing the web service. Source