I'm sure this depends entirely on the states you're going through, but here's what happened to me:
A friend sold me his old Explorer, last registered in IL, we were both living in MA at the time. Plate had expired, car sat around awhile. I ended up having to move back to IL from MA. Figured with a title and fresh bill of sale in hand I could explain my way out of any stops to question it. I made it about 2 miles. Got stopped and my *** chewed out by a state trooper (who didn't have any response to the "Well what should I have done instead?" question), had my car towed (with all of my possessions inside), and was dropped at the next rest stop.
So I really have nothing to offer as far as help, but I would not recommend driving with no plate whatsoever - thinking back I'm thankful I didn't make it far at all, and wonder what would have happened if I was in the middle of New York or Ohio and had the same thing happen hundreds of miles from anyone I knew.