Well, thanks to a privacy document that Microsoft has posted to its website, we now know at least two flavors that Windows 7 will come in.
The information is contained in the Windows 7 Pre-release (M3) Privacy Supplement.
BitLocker Drive Encryption (BitLocker) is available on computers running Windows 7 Enterprise Edition and Windows 7 Ultimate Edition. Should your computer be lost or stolen, BitLocker protects your data by helping to prevent offline software attacks. Turning on BitLocker encrypts the hard drive where Windows is installed, including all information that is stored on that drive. [Emphasis added]
Anyone want to take bets on whether the Ultimate SKU will offer "Ultimate Extras" as one of the benefits of going Ultimate? ;) I doubt it!
(Hat tip to Long Zheng for finding the privacy document.)