This is big news. Since we started using the TFS Scrum template at work, I've always been frustrated that there is no way to write a query that filters by current iteration. You can filter to a specific iteration, but then you have to keep updating that query every time you end one sprint and start another. It's a very basic piece of functionality missing from the query language.
Until now. Two weeks ago, Microsoft announced that they're releasing a query token called
@CurrentIteration that can be used to in queries.
Unfortunately, I couldn't find any information on when this will come to the on-premises version of TFS. It's been rolled out to Visual Studio Online, so I expect it'll be included in a release soon. In the meantime, I'll continue to use the TFS Monitor we wrote at work to quickly find outstanding work items in the current sprint (more about that here).