Okay well... the first question is 'how?' The movies were never intended to be shown in 3D and weren't filmed that way- even the 'new' ones are just regular old fashioned films. I think the second question is 'why?'
Everyone's seen these movies dozens of times and to drop them back into theatres again... maybe it's just me. And one more thing (Now I feel like Steve Jobs)- the movies will be released in order. 'In order' means #1 through #6. So the whole 3D love fest will kick off with none other than everybody's least favorite episode- The Phantom Menace.
Boom.
Star Wars dot com