A couple of months ago, Mark Anbinder mentioned in "Boot Camp Beta on the Chopping Block" (2007-10-14) that, per Apple's repeated statements, the beta period for Boot Camp would officially come to an end once Mac OS X 10.5 Leopard was released. Apple's plan had always been to beta-test Boot Camp under Tiger, but then - once the feature was built into Leopard - discontinue support of the beta. On 28-Nov-07, Apple sent an email message to all those who had provided their addresses when downloading the Boot Camp beta, with a gentle reminder: If you haven't already upgraded to Leopard and want to continue using Boot Camp, you'd better get with it now, because the beta version will officially expire on 31-Dec-07.
If you've already upgraded to Leopard, or plan to do so before the end of the month, you have nothing to worry about; Boot Camp should continue working seamlessly after you transition to 10.5. If, however, you're still using Boot Camp and Leopard isn't in your immediate future, you should understand what Apple means by the word "expire."
If your Mac's clock ticks over to 01-Jan-08 and you still have Windows installed under the Boot Camp beta in Tiger, it won't suddenly stop working. Your files won't disappear, and you'll still be able to boot into Windows. What will change is that the Boot Camp Assistant utility will no longer run. That means you won't be able to create new Boot Camp installations, but it also means you won't be able to remove your existing Boot Camp partition without mucking around in Disk Utility or Terminal and, in all probability, erasing everything on your disk.
This situation mirrors what Apple previously did with early beta versions of Boot Camp: If you had version 1.2 or earlier installed, it expired on 30-Sep-07, requiring an upgrade either to version 1.3 or 1.4 (neither of which remains available now) or an upgrade to Leopard. If you happened to fall through the cracks by not upgrading to a newer beta before the old version expired, however, Apple provided instructions for removing a Windows partition - basically, set your Mac's clock back to a time before the beta expired, run Boot Camp Assistant to remove the Windows partition, and then reset your clock to the current time. I presume the same procedure will work with beta versions 1.3 and 1.4 after 31-Dec-07, but I still recommend upgrading to Leopard or removing your Windows partition before then, if possible.
For those who have decided to switch from Boot Camp to virtualization software, it is possible (though not necessarily easy) to migrate your installation of Windows from Boot Camp to a virtual machine. In Parallels Desktop, use the included Parallels Transporter utility; instructions are found in the Parallels Transporter User Guide on pages 37-38. VMware Fusion users will need the separate (free) VMware Converter utility, which runs under Windows. After installing it, you'll need to turn on Windows File Sharing in Mac OS X, open your Boot Camp partition in Fusion, and then run the converter, saving a copy of your Windows installation to a new disk image on your shared Mac volume.