It has been blogged on other, typically good, Yankee blog sites (http://riveraveblues.com/2007/11/10/the-man-who-just-wont-retire/) that Bernie should just hang 'em up and forgo any further 'come back' talk.
Bernie is the classiest Yankee I have ever seen. He is among the MOST important reasons that the Yanks of the '90's were as dominant as any team in baseball history.
I'll say what I've been thinking for about a year now- Bernie should have had the opportunity, and still deserves the opportunity, to leave the game on his own terms. Not giving Bernie a 1 year deal last year was as bad a decision Cashman has made in his tenure as GM.
If the team has the opportunity to remedy that decision this year, I say give Bernie back his dignity, sign him for 1 year and let him go out the very way he represented the team for so many years- with grace and dignity and as one of the greatest to ever wear the pinstripes.