Mathematica 10 works with Workbench v2.
Using a recommendation from a Wolfram support person here http://mathematica.stackexchange.com/q/69567/66 , this is what I do to get it working.
Install Eclipse and Workbench
Install Mathematica 9
Run a debug session from Workbench with Mathematica 9 (adjust the path of the kernel)
Install Mathematica 10
Run a debug session from Workbench with Mathematica 10 (adjust the path of the kernel)
Uninstall Mathematica 9
You can then use Egit with Github for code versioning and Mylyn with Github (for example) for bug tracking, it's a great combination of tools. You can also use Gitlab instead of Github.
I hope Workbench 3 will one day come to official life. You can't get it though as a plugin from the support (if you have a Premier license), it's just as a standalone version. And with the standalone version you can't install all the Eclipse plugins, so I prefer to still use Workbench v2,