From Blues News, in a concise press release, id Software is planning to release/announce (?) new games at QuakeCon in August:
NEW GAMES FROM ID SOFTWARE.
QUAKECON 2001
AUG. 9 - 12 -- MESQUITE, TEXAS
A follow up press release localizes it to Aug 10th. As you must know, Carmack has always been a strong proponent of NeXTStep and subsequently Mac OS X. Presumably, any new games from id would also be released on OS X. Whether this assumption is true or not, we'll see in August...