I recently found this, I wrote it about 1998 or 1999.
15 year lifetime of the desktop OS
1975 – CP/M rules
1980 – CP/M rules, DOS introduced
1985 – DOS rules, CP/M is dead
1990 – DOS rules, Win3.1/95 introduced
1995 – Win3.1/95 rules, DOS is dead
2000 – Win3.1/95 rules, ??? introduced
2005 – ??? rules, Win3.1/95 is dead
Microsoft introduced both DOS and Win3.1/95 and pushed them. Microsoft really doesn’t have any reason to do that again. The only new thing on the horizon is Win2000, with Microsoft push that and kill Win3.1/95?
Win2000/XP did actually kill off Win3.1/95 more or less right on schedule, that was a complete surprise. By this schedule, we should see the successor to WinXP come along in a year or two. I wouldn’t count Vista, it is a continuation of the Win2000/XP codebase. Maybe a Web 2.0 thing like Google Desktop perhaps? We should also expect Win2000/XP/Vista to be gone by 2015.