It's just rumours so far, but someone over on the dandom.com guestbook proudly labelling himself (herself?) In the know, has posted what is said to be the Steely Dan tour dates for May:
* May 6th New Orleans, Louisianna
* May 12th Orlando, Florida
May 18th Wallingford, Connecticut
* May 24th Upper Darby, Pennsylvania
May 29th Boston, Massachusetts
May 30th Boston, Massachusetts
* = previously officially announced dates. He/she also adds that
"you will soon see dates added for NYC - 2 nights, DC, and maybe ATL."
So there you have it. As always; keep an eye on steelydan.com for the official tour dates.