When Cars came out in 2006 it was the first Pixar film rendered in high definition (in this case, 2048x1024 pixels). All previous Pixar films and most other CGI movies (like the Dreamworks titles) had been rendered at or around DVD resolution (typically 720x480). So, despite viewing them on a big screen in a movie theater, the actual detail of previous Pixar movies was little better than you could get on a standard (pre high-definition) TV.
About that time I conjectured to some of my colleagues that, since Pixar movies are rendered from 3-D digital models, they could be re-rendered at higher resolution or even with 3-D effects. Sure enough, Pixar has done just that. The original Toy Story and Toy Story 2 are being re-rendered at high resolution and in 3-D. The release will be limited to two weeks as a double feature.
Of course, it's a promo intended to generate interest in next June's release of Toy Story 3 which will also be 3-D. Presumably Disney will follow up with a Blu-Ray high definition release of the two titles.