Here is some more info from the Daizenshuu EX site, go there for all your dragonball needs
The opening stuff is the standard fare we have come to expect from the earlier announcements (like "Commemorating the 20th Anniversary of the Start of Dragon Ball Z's Broadcast!" and "The Son Goku Legend, Once More!! And its name is... DRAGON BALL KAI"). However, the interesting material appears under the header "The four points that make up the world of "Kai"!":
The story will be developed speedily!
"Kai" starts from the invasion of the Saiyans. This version will be re-edited to hew more closely to Akira Toriyama's original story, so the story's development will progress all the faster!
The opening and ending songs will be completely renewed!!
The opening and ending songs will together be made anew! Furthermore, in "Kai", the background music will be newly recorded. Let's enjoy "Kai", where even the music has been powered up!!
Through digital processing, the image will be made vibrant!!
All the grime, damage and noise remaining on the "Z" film will be removed! In HD, the image will be even clearer. We've carefully made the ultra-powerful "Kai" world even more impressive!
An all-star voice cast will record the lines anew!!
The original main cast, centered around Masako Nozawa as Son Goku, will reunite, yo. They'll breathe life into the characters again, to support their appeal!!