Or they could just use the same disclaimer that they use for 4 GiB.
Well, that's not really tenable once you go up to 6 or 8.
This whole problem just "goes away" once OEMs
1. Only use motherboards that support memory reclaiming, and turn it on by default
2. Ship with a 64bit OS.
At this point, driver compatibility for in-the-box hardware is no longer a concern. There may be the odd expansion card option that doesn't have a 64bit driver, but Dell can either flag that as requiring you to opt for 32bit (they already have OS-specific hardware options on their website) or just lean on their component suppliers to get with the program. (If you're supplying Dell, and they say they're going to drop one of your products unless you jump through a hoop, you darn well jump through the hoop).
Application compatibility isn't a big deal either, in most cases. There are some 16bit games and whatnot out there still, but they're pretty rare in the consumer world anymore (and Dell could always strike a deal with the DOSBox people or whatever). But 32bit apps for the most part run fine, so there's no reason to be waiting on 64bit applications.
The real issue for the OEMs are the installed base of outboard peripherals -- printers, scanners, cameras, phones, MP3 players, etc -- that users may have bought years ago and still happily use... and expect to work with their new machine. There may be no 64bit driver for those, and in many cases there may be no prospect of getting one for what is now an unsupported product. Which, frankly, tells me that there's no point in the OEMs waiting: the situation is not going to get appreciably better. At this point they should, at the very least, offer 64bit as an option
. (Dell gives you all sorts of OS options -- business or home or ultimate, XP or Vista, even Windows or Linux -- but no option for 64bit pre-installed as far as I can tell). When you choose 4GB of memory (or more, soon) they should recommend it. And by next year it should be the default option.
I know the OEMs, and Microsoft, are dreading the flood of support calls they're going to get when Joe Consumer gets his new PC and his old printer doesn't work, but they're going to have to deal with it eventually.