Arduino on Xcode Project — Official Thread

ScottG:
Just so I'm clear on updating projects to the latest embedxcode version - if my project is rev 108 or higher, then when new versions of embedxcode come out, I can update that project to the latest embedxcode version. But projects 107 or lower are not updatable, is that correct?

That's correct.

Starting release 108, the template includes a utility to manage and update the projects created with it.