Lee, there have been many other converted films released to theaters already. These include:
SUPERMAN RETURNS (4 sequences in IMAX version)
HARRY POTTER AND THE ORDER OF THE PHOENIX (last 20 mins in IMAX version)
HARRY POTTER AND THE HALF BLOOD PRINCE (first 10 mins in IMAX version)
NIGHT OF THE LIVING DEAD (1968 colorized version) was converted to 3-D and recently debuted in an outdoor LA screening.
PIRANHA 3-D was shot flat and is undergoing a conversion (this was intended from the outset, as was the case with ALICE IN WONDERLAND.)
There are plenty more in process, both catalog and yet to be released movies. Some IMAX documentaries have undergone conversion as well. Look for more and more movies to be planned as 2-D to 3-D conversions all along; some directors apparently feel this is the easier way to go. I've heard talk that the new CONAN and FLASH GORDON projects will take this route.