I had just installed a fresh copy of Visual Studio 2012 and i also installed the latest Update 4. I tried to open my Visual Studio solution in it. I gave me a message project type not supported message.
It tried creating a new sharepoint project but it was missing, which must usually visible like in the below image
What i found out is that we need to install Microsoft Office Developer Tools for Visual Studio. It is an add-in for Visual Studio that enables developers to create, build, debug, run and publish apps and solutions for Office and Sharepoint. The Web Platform Installer usually installs it for you.
Once you are done downloading, double click to install the app and you will find the options to create sharepoint apps.