I personally don't see McCallum's comments becoming a reality. If they have spent the money on the conversion, then they will just release them anyway. Sure it may be like what Matt suggests which is an accelerated schedule, but they will all see theatrical release.
The biggest motivator to me is the fact that having each of the movies in the theater again offers them another shot at merchandising the heck out of each movie, which is where the real money is.
Look at all the stuff Hasbro has planned for EP1, which up until now, has pretty much been the pariah episode as far as the toys go for quite some time. Sure we've had a few figures here or there and the Saga Collection 2 had a TPM wave, but that's about it and with the exception of EP1, I can see Hasbro using these 3D re-releases as a means of making some larger "parking lot" items for each movie, bolstered by the fact that there will be extra exposure from the 3D re-release.
I think they will easily be able to pull in ~$20 million for each movie. Especially if they get them shown in some of the IMAX theaters - I know that's where I'm going to go see them when they come out.
What has me the most disappointed about McCallum's comments is the implication that they are all done and ready to go. If that is the case, then they only made 3D versions of the existing versions of the movies. I was hoping that they might actually be adding some new stuff to truly make going to see these new 3D versions worthwhile.