Actually, I'm sure Jeff Hardy is the only wrestler who is left that can still win the Grand Slam under it's original definition(since the European Title is no longer around) if he ever wins the WWE Title. Also, Im sure you can replace the WCW Belts w/ their WWF/E counterparts as substitutes.
Like the U.S. Title could sub for the IC Title, The WWE Tag Belts(WCW) could sub for World Tag Team(WWF/E), World Heavyweight for WWE Title