http://stackoverflow.com/questions/13054212/vs-2012-ef-5-0-update-model-from-database-not-picking-up-table-changes
Yes, this still works in VS2012. Are you using the default code generation or do you have a TT file? It could be that it's being added to the EDMX but your class files are not being updated.
Try right-clicking on the EDMX file or the relevant TT file in Solution Explorer and choose "Run Custom Tool" to make sure it's being regenerated.