Favre might not be the most trustworthy source on Brett Favre at this point, but he did file retirement paperwork with the NFL in January. And, well, Is Brett Favre Retiring? still indicates that Brett Favre is retiring.
Here's the original story from AP:
Favre says he likes dealing with young players, "but in what capacity, I'm not really sure yet." He says he has enjoyed staying around Southern Miss but has "no plans right now and we'll see where that takes me."