If they haven't defected yet and have remained Democrats even though their party is in the minority (and do remember that Cramer has been in the House throughout the House Democrats wilderness years) why on earth would they wait until their party was back in the majority again?
The time to defect is when the party you are defecting to is in the ascendency, not when it's trying to cling onto power.
Wouldn't they be enticed by an offer of a chairmanship and increased power in a Republican House? As Ken Mehlman gleefully points out, the Democrats would chair the major committee are old, liberal and live in safe districts.
A desperate Republican House leadership may be more willing to provide real power to the Cuellar's and Cramer's of the House than liberal Pelosi is.