Paul Cornell writing a Doctor Who crossover for Titan

Saw this on CBR:
Paul Cornell to Write Major "Doctor Who" Crossover
http://www.comicbookresources.com/?page=article&id=59421

"For the first time in any media, Titan Comics will combine the forces of the Tenth, Eleventh and Twelfth Doctors in a five-part crossover event running from mid-August until the end of September. The story will run in place of the currently ongoing "Doctor Who: The Tenth Doctor," "Doctor Who: The Eleventh Doctor" and "Doctor Who: The Twelfth Doctor" series for the duration of the event.

As revealed by the The Hollywood Reporter, comics writer Paul Cornell -- who has contributed to multiple aspects of the "Who" franchise over the years -- will tackle the event, uniting three of the twelve regenerations of the Doctor from BBC's longest-running sci=fi television series. Cornell has written for the "Doctor Who" television show in the past, penning episodes "Father’s Day," "Human Nature" and "Family of Blood" as well as the Hugo Award-nominated "The Girl Who Loved Doctor Who" one-shot comic.

Though there aren't very many details available about the plot, the crossover will pick up from ongoing comics storylines and feature current TV companion Clara Oswald, plus comic book originals like Gabriella Gonzalez and Alice Obiefune. On television, the Tenth Doctor was played by David Tennant, the Eleventh Doctor by Matt Smith and the Twelfth and current incarnation is portrayed by Peter Capaldi.

This "Doctor Who" crossover is scheduled to start on Aug. 12."

Cool! I bet the Twelfth Doctor makes fun of the other two.

Looking forward to this immensely! but why no other Doctors?