According to one user supplied report, Apple has reportedly filed for a patent for a rotating display, allowing both vertical and horizontal alignments from a single screen. From the summary:
This invention relates generally to a processor-controlled system such as a computer system and, more particularly, but not exclusively, to an electrical arrangement in the system for managing video information for rotating computer display images.
The patent description reportedly appeared on LexisNexus' service dated March 23, 2004, but does not appear to be locatable in the US Patent Office site at the moment.
While pivoting displays have been marketed in the past (Radius Pivot), Apple has never offered one of their own.
Readers are cautioned, however, that this particular patent, however, may simply represent Newton technology patents finally becoming processed. The patent summary notes that the rotation feature would be "especially advantageous for pen-based and hand-held computers". Apple's Newton 2x00 handheld computer did allow for this same portrait and landscape rotation.