Mac OS X 10.4: Tiger
According to MacMagazine.com.br (Portuguese), the upcoming Mac OS X update (10.4) will be known as "Tiger".
Apple has used similar feline names for previous versions of Mac OS X: 10.3 (Panther), 10.2 (Jaguar). In July, Apple registered a number of related trademarks: Lynx, Cougar, Leopard, and Tiger.
MacMagazine.com.br also reports that up until this point, 10.4 was known as "Merlot" internally. This is consistent with information available from MacRumors' sources.
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