In short no. Loki, anyone? Only port if porting is trivial otherwise don't waste your company's resources.
Of course you could always run development on a *nix platform with some of the standard/open libraries such as OpenGL, SDL, Allegro, etc. That would almost insure that your software/game ran on various platforms, for instance Mac, *BSD, GNU/Linux, Solaris, MS, QNX, Handhelds, etc.
Mi dos centavos.