Actually, Evander may have held onto the cruiser title for 12 years or more before losing. The Nate Miller type guys weren't going to beat him and then you had Cole and Gomez having nice cruiser runs. I think Evander has a Joe Louis run at cruiser before dropping a close decision to the southpaw JC Gomez. And then winning the rematch. I don't think any of the lh would have been stepping up to fight him either and would not have had much success with that workrate/toughness/conditioning of Commander Vander at cruiser.
Maybe Holy could only manage to make the 190lb limit for another couple of years, then he retires still the Undisputed Cruiserweight Champion, with probably 6 or 9 unified title defenses for 2 or 3 years following the De Leon fight. The most important implication of Holy not moving up, is Douglas would absolutely have to give Tyson a rematch. Who else is going to get him purse like $28mill for a title defense? Nobody, except Tyson. Anyway, Mike still is hooked up with Giachetti rather than Patterson (Dung King's choice), then blasts out Tillman & Stewart to get his confidence back, as before. But instead of facing Razor Ruddock, the physically & mentally supremely conditioned Mighty Mike faces Douglas in the rematch he always wanted. Ripping brutal bodyshots to Buster's body, he takes away his legs, en-route to a mid-round stoppage (if Douglas is in-shape) or an early one (if he's not). The explosiveness, extra activity level, & willingness to go to the body will be the difference here. Buster wouldn't be a facing a listless & lethargic lump, who throws a pathetic 19 punches a round, all loaded-up with a long-fuse for the head.
if he'd stayed, his undefeated 25 defence record in cruiser would be unbroken for maybe 150 years or more.