Hmm...it's hard to tell when they're gonna up the base number. Here's a plotting of all the revisions to the Mac OS:
1984 - 1.0, 1.1
1985 - 2.0, 2.1
1986 - 3.0, 3.1, 3.2
1987 - 3.3, 4.0, 4.1, 4.2, 5.0, 4.3, 5.1
1988 - 6.0, 6.0.1
1989 - 6.0.2, 6.0.3, 6.0.4
1990 - 6.0.5, 6.0.6, 6.0.7, 6.0.8, 6.0.8L
1991 - 7.0, 7.0.1
1992 - 7.0.1P, 7.1
1993 - 7.1P, 7.1P2, 7.1P6
1994 - 7.1.1, 7.1.1s, 7.1.2, 7.1.2P, 7.5
1995 - 7.5.1, 7.5.2
1996 - 7.5.3, 7.5.4, 7.5.5
1997 - 7.6, 7.6.1, 8.0
1998 - 8.1, 8.1j, 8.1i, 8.5, 8.5.1
1999 - X Server 1.0, 8.6, X Server 1.1, 9.0
2000 - X Server 1.2, 9.0.4, OS X Public Beta
2001 - OS X 10.0, 10.0.1, 10.0.2, 10.0.3, 10.0.4, 9.2, 10.1, 9.2.1, 10.1.1, 10.1.2, 9.2.2
2002 - OS X 10.1.3, 10.1.4, 10.1.5, 10.2, 10.2.1, 10.2.2
2003 - 10.2.3, 10.2.4, 10.2.5, 10.2.6
Personal notes here - I started using Macs with OS 7.1 (probably one of those "P" ones, it was on a Performa) - been using 'em since. I also didn't get OS X until after the public beta...and missed out on all the updates from end of 2001 and all of 2002 due to not having an internet connection. I was stuck at 10.1.2 until I bought 10.2.1 (it was a little after 10.2 came out, so the stores were selling 10.2.1 at the time)...was stuck at that until I finally got back online in Feb this year and updated to 10.2.3...then almost immediately to 10.2.4.
You guys should check out the site I got that from - it has tons of information on it, not just release dates. Also has developer releases and info on what Macs the stuff installed on to.
Erm...don't wanna go against the board rules, so I won't post the link, but do a google search for Mac OS History. It's the first result that shows up (for me at least).
'Case anyone's wondering, I posted all of that just to show there's no knowing when Apple is gonna bump it up to the next OS version.
Plus, the nostalgia is nice.