I would love to see HBO making a Justice League series. I know super hero on TV never worked very well and that DC don`t want those powerhouses on TV, but I think Games Of Thrones is such a milestone for TV production, proving that television can produce top notch productions. Maybe not a Justice League series, but a true Batman, Superman or Wonder Woman would be great.
Other dream sereis for me would be Harry Potter show, but J.K. Rowling already told it isn`t happening.