TFS allows you to update work items in bulk by applying a template to them. Here’s how:
1) Install the TFS Power Tools
2) Right click on Work Item Templates in Team Explorer and select New Template
3) Select your work item type:
4) Fill out the fields that you want to change. For this template I wanted to bulk items items to change their State to Not Started
5) Run a query that contains all the items that you want to apply the template to then select the items.
6) Right click and choose Apply Template…
7) Select the template you want to apply.
8) Click OK. As you can see below the State of these items has been updated to Not Started
9) Click Save