from 1999. D&D is under Hasbro and they didn't buy WotC just for flavor, but for profit.
Also from former editions the time scale between edition is reducing.
AD&D(1st ed) 1977
AD&D(2nd ed) 1989 - 12y
AD&D(2nd ed revised or 2.5e) 1995 - 6y
3.0E 2000 - 5y
trend is to reduce the time between editions.
There is no 2.5. The reissue of the 2e PHB & DMG with new layouts and trade dress (and the accompanying new cover for the MM, which was otherwise unchanged) did not change the core rules of the edition; the text was identical. The Players Option series that followed were just that: options, suggested variant rules that one could use, but never assumed to actually be in use by any other product, especially since it's actually impossible to use all of the options at once due to incompatibilities with changes made by them. They do not constitute a new .5 edition, and actually were largely unpopular. Only a few ideas had legs, and they wound up in 3e.