I am using the preview version of the SharePoint 2013 Developer tools and I didn’t see an option that allows upgrading SharePoint 2010 projects to 2013. Following some tweaking I discovered a quick way of converting projects from 2010 to 2013.
Step 1: Open your csproj with a text editor.
Step 2: Change the Target Framework Version from v3.5 to v4.5.
Step 3: Set the Office Target Version to 15 by entering the following tag to the file.
Step 4: Update all referenced assemblies;
- SharePoint assemblies from version 22.214.171.124 to 126.96.36.199
- .NET assemblies from 2.0 and 3.5 to 4.0 and 4.5
Step 5: Build the project to check for any compilation errors and re-adjust.
Keep in mind that your existing list definitions will need updating to take advantage of the new view styles.
Update: The SharePoint team took all the fun away by providing Visual Studio Solution upgrades with the latest Office for Visual Studio Tools (feb-2013).