I don't have concrete evidence of this, but I heard a rumor that Tony Hawk Pro Skater was supposed to happen in the year 2000 but Bally/Williams closed its doors. Supposedly they had an agreement in place that every 10 years was going to be a new skateboarding game. (1980 was Skateball, 1990 was Radical, 2000 would have been Tony Hawk). But that could also be entirely BS since I can't find any documentation to back it up.