This is the Woody Guthrie Centennial (1912-2012).
Bob Dylan visited his hero for the first time on January 24th 1961 in Greystone Hospital. Woody gave him a card on witch he wrote "I ain't dead yet" to show the folks in Greenwich Village.
Now, in the Woody Guthrie Centennial, Bob uses the phrase in Early Roman Kings on his new Tempest album. As there is more in the lyrics to believe the song isn't about the ancient Roman kings who left their footprints everywhere among the rubble filled streets of Rome, this direct citation directs the way for a possible interpretation.
Clear enough to baptize the US Summer Tour 2012 with that same phrase.
Links to lossless recordings of the tour can be found in the Tour List
A sticker with the same words can be found in the Woody Guthrie Store