According to an article on CNet, Opera has decided that they need to make a Macintosh browser after all.

Citing a new cross-platform development architecture, they indicate it is now easy for them to make a Macintosh version, so why not produce one (which I believe is what we said on this site when the original withdrawal occurred).

Says a spokesman for Opera, "We still believe that people on the Mac platform deserve choice, and they deserve quality. So we want to provide it to them."