That part of the analogy actually works too. Without a gaming group and ruleset (analogous to the computer and OS), you are cut off from most gaming.
Now, with a computer you can be behind by several OS revisions and still function just fine (I write on my computer running Windows 2000 PRO that was running Win 98 and working just fine until two years ago). You may not be able to run the latest games and applications, but early adopters often face the same problem in the first year or two after an OS comes out. Similarly, with a gaming group, you can continue to play the old system and get by just fine. You may not be able to play the newest modules from WotC but early adopters will find that their selection of modules is also quite limited. Really, the big thing that you'll be missing out on is the RPGA's Living campaigns (and the 3.5 ones will be continuing for some 6 mo or so after 4e comes out so you don't have to switch immediately even there). Since a lot of people can take or leave them, you're not necessarily missing out on anything. (As the writer of a number of Living Greyhawk modules, I think you'd be missing out on something worthwhile right now, but I don't yet know whether 4e will support the kind of adventures I enjoy, so I can't rate how valuable that is, even to me).
With a computer, the only real reason to upgrade the OS is because
A. the new OS offers features and support that your current one doesn't
B. There are some great new applications/games on the new OS that your current one doesn't support
C. You're getting a new computer anyway and might as well get the new OS as the old one.
Within the analogy, C won't apply unless your collection of books is lost, stolen, or destroyed--and perhaps the rest of your gaming groups' books as well.
A. Only applies if 4e actually turns out to be significantly better than 3.5
B. Only applies if some incredible module is released for 4e, all the commercial offerings switch to 4e, or your gaming group as a whole decides to switch to 4e.
My own take is that from 2e to 3.x, there was an extremely strong motivation A to switch. My own experience and those of others from the boards seems to be that no-one was running 2e without tons of house rules, most of which were rendered unnecessary by 3.x. Thus it was that most people appear to have made the switch quite quickly and created a very strong motivation B for adopting the third edition ruleset for the remainder of the gaming populace.
My impression of the current situation, however, is that there is not really too much of a motivation A for the switch. Other than the epic 6 houserule set (which will still be a houserule set under 4e since designer comments indicate that 4e is still going to retain the features of 3.x that epic 6 is designed to eliminate), I don't see extensive lists of houserules in peoples' 3.x games. (I have used a number of houserules in my own campaign, but they are for flavor rather than balance and gameplay reasons and I don't forsee 4e eliminating the need for them, unlike 3e which I saw and thought "wow, it's like it's got all my houserules built in and done better). Thus my impression is that, unless 4e is even better than the considerable hype and marketing-speak suggests, there won't be much of a motivation A for the switch. Some people will switch early, but I expect there to be a substantial community of 3.x players for some time; the community will probably persist long enough to still be strong when WotC decides to release 5th edition.
At that point, a lot of people may be ready to make the switch, both from reason A (as 5th edition should incorporate all the fixes that 4e needs as well as the ones 3.x needed), and reason C (since peoples' books will be getting worn out by then), and 5th edition will probably stand a chance of gaining a majority share of the D&D marketplace. For the moment, however, my money is on 4e turning out to be the Windows ME of the RPG world--it gets a bit of traction, but doesn't displace the previous systems as home users, by and large, continue to use Win 98 and later switch to the Windows XP product while business users largely maintain the use of Windows NT and then upgrade, piecemeal to Win 2000 or Windows XP.
Li Shenron said:
The comparison between D&D and Windows makes me depressed
There is also one thing you forgot: without a computer and its operating system, you're cutting yourself off from a lot of things. It's hard to say "no" to owning a computer nowadays. And if you want a computer, you must have the latest Windows (I know, there's Linux, but that's not so common among people that aren't very much into personalizing their computers) or most of the software won't work properly. That is not the case with D&D... you don't need the latest to be able to play. Plus, you don't even need D&D to play a RPG, there are hundreds to choose from!