(Updated March 8th to note the final 1.2.15 was released).
SDL 1.2.15 final release is out. I have tested it with Supermodel 0.2a on Mac OS X Lion and it fixes -fullscreen to work again (woohoo!)
Get it [http://www.libsdl.org/download-1.2.php]here[/url]. Download SDL-1.2.15.dmg, open the .dmg file, then drag the SDL.framework folder into your /Library/Frameworks folder like before. Choose to overwrite all files, and you should be good to go.